PALOMARES, Spain >> Jose Manuel Gonzalez Navarro, a mechanic, headed out of this seaside village on his motorbike one morning 50 years ago when he heard explosions overhead and looked up to see a ball of fire in the sky. Debris started to shower down, some “falling very slowly, like if a giant tree was shedding shiny metal leaves,” he recalled in an interview.

Gonzalez Navarro turned around and sped home to check that his house was not hit. He later drove back to where he had seen debris land and found an undetonated bomb attached to a parachute. He cut off the straps of the parachute and took them home, along with some work tools and bolts that he found scattered on the ground.

“I was just thinking about what objects might prove useful,” he said. “I liked fishing, and those parachute straps, thin but very solid, were clearly perfect to be turned into a weight belt for diving.”

Like many in Palomares, Gonzalez Navarro, now 71, figured he had witnessed a military air crash. But he was unaware that a U.S. Air Force bomber and a refueling jet had collided, sending four hydrogen bombs hurtling toward Palomares. Although no warheads detonated, two of the bombs shattered, spreading plutonium over the village.

Whereas U.S. service members are complaining that the hurried cleanup effort carried out by the military jeopardized their health, many in Palomares lament the damage the incident has done to their community.

“Living in a radioactive site that nobody really has wanted to clean has brought us a lot of bad publicity and has been something hanging over our head like a sword of Damocles,” said Juan Jose Perez Celdran, a former mayor of Palomares. For years after the crash, local tomatoes, lettuce and watermelons did not carry any Palomares label because of the stigma associated with the place.

And the cleanup effort continues half a century later.

In 1966, U.S. troops removed about 5,000 barrels of contaminated soil after the accident and called the cleanup complete. But about a decade ago, the Spanish authorities found elevated levels of plutonium over about 99 acres. Some of the areas of elevated radioactivity almost touched private homes, as well as fields and greenhouses. Scientists from CIEMAT, the Spanish nuclear agency, fenced off the most hazardous sections and began pressuring the United States to remove about 65,000 cubic yards of radioactive soil — far more than was removed right after the crash.

In 2009, Foreign Minister Miguel Angel Moratinos of Spain sent a confidential note to Secretary of State Hillary Clinton warning that Spanish public opinion could turn anti-American if Spain disclosed a Palomares contamination study, according to a note contained in the WikiLeaks documents and published at the time by the newspaper El Pais. In early 2011, Spain’s foreign minister at the time, Trinidad Jimenez, told the Spanish Senate that cleaning up Palomares was “a priority.”

In October, Secretary of State John Kerry signed a memorandum of understanding in Madrid promising to finally return Palomares to its pre-1966 state.

Spain and the United States agree that about half a kilogram, or about 1.1 pounds, of plutonium remains in the area — a significant amount since less than a microgram can cause cancer — and the Department of Energy has agreed to remove the soil and bring it back to a nuclear storage facility in the United States. A formal agreement on the size of the cleanup, when it will start and who will pay is still in the works.

The long-term health consequences of the accident for Palomares residents remain murky.

Many inhabitants consider the warnings of radiation overblown, but others take a cynical view of why the U.S. and Spanish authorities have let them live in a contaminated area for decades. “They’re just using us as guinea pigs, to see what happens to people who live in a contaminated area,” Francisco Sabiote, a plumber, said. “They tell us all is fine, but also that more soil needs to be taken away. So if that is really needed, why all this waiting?”

The day of the crash, another bomb was found by Martin Moreno, 81, who headed toward the cemetery with a friend after seeing the collision overhead. They first spotted a U.S. pilot apparently sitting on the ground. When they got closer, however, the pilot turned out to be dead.

Moreno then climbed on top of the bomb to figure out what it was. “It looked like a strange and yellowish casket, with a gash on the side,” he said. Using a screwdriver, he tried to cut it open, to no avail. “We wanted to take out a chunk, but it was just too hard to break off,” said Moreno, who added that he was in good health.

Of the 11 crew members on the two U.S. planes, seven were killed. But for most villagers, what prevailed was not a sense of tragedy but a mix of bewilderment and relief at having been spared a direct hit. And once U.S. service members took charge in Palomares, sharing their cigarettes and beers with the villagers, “this almost became a party atmosphere,” Gonzalez Navarro said.

U.S. officials feared that evacuating the area would create what the lead Atomic Energy Commission scientist on the ground at the time called a “psychological monument” to the accident, so they let villagers stay, assuring them that no radiation had been released. They issued vague instructions and warnings to residents while offering words of reassurance and financial compensation to farmers for their lost harvests. The villagers, in any case, were just too poor to prioritize health concerns over economic issues.

“We were told that we should perhaps get rid of what we had been wearing that day, or at least wash it thoroughly, but of course nobody here could afford to throw away clothing,” Gonzalez Navarro said.

Since the crash, a sample of the 1,700 residents of Palomares has been checked each year for radioactivity in Madrid, under the supervision of the federal nuclear agency. Maribel Alarcon, a town hall official, said that the recommendation from Madrid was that each resident be tested every three years. She last got checked three years ago, testing negative.

Many residents, however, said they had stopped getting tested more than a decade ago. Sabiote, 27, said he last traveled to Madrid for a medical examination when he was 12 and had no plans to return. “We all have to die one day of something,” he said, shrugging his shoulders.

Antonio Fernandez Liria, the mayor of Cuevas del Almanzora, a neighboring town under whose political jurisdiction Palomares falls, said the medical tests showed that “we’re not the Martians that some people believe we should have become.”

Spain’s nuclear agency says that the results of the medical checks do not show high levels of plutonium contamination and that the frequency of cancer around Palomares is similar to that in other towns.

“If a test had shown positive, do you really think we would still be living here?” said Diego Simon, who runs the local stationery store.

Some Spanish scientists have carried out their own studies on the Palomares population, but also without finding evidence that should raise the alarm. After struggling to get access to the relevant data, Pedro Antonio Martinez Pinilla, an epidemiologist, published a study in 2005 that found higher incidences of cancer, but he concluded because of the small sample size that no correlation could be drawn between living in Palomares and incidences of cancer.

Jose Herrera Plaza, a Spanish journalist who recently published a book about Palomares, said the crash had a profound psychological “hibakusha impact,” the term used to refer to survivors of the U.S. nuclear bombs dropped on Japan in 1945.

“All the communities that deal with contamination, independent of whether we can prove actual health problems or not, suffer and live with a permanent paranoia,” he said.

The 1966 cleanup of Palomares was not only incomplete but might also have spread the contamination further. For instance, local officials said, the decision to burn contaminated tomato crops might have helped spread dangerous particles in the air.

“I think that things were done with the technical knowledge available at the time and the political situation in Spain at the time,” said Yolanda Benito, an official from Spain’s nuclear agency. “Spain was a dictatorship, so it was not the most transparent government in the world.”

© 2016 The New York Times Company