LINCOLN, Calif. >> Firefighters on Wednesday will try to siphon propane from a burning rail car in a bold maneuver meant to head off an explosion after the blaze forced the evacuation of thousands of people in a Sacramento suburb.

Officials decided to take the step after consulting with members of a national response team from Houston, who were flown in overnight to offer advice, Lincoln Fire Chief Dave Whitt said.

Fire officials initially said the blaze could continue for 21 days, but Whitt said that scenario was unacceptable. Between 4,000 and 5,000 homes in the city of 40,000 are evacuated and more than 6,000 students are missing their first days of classes, with district schools ordered closed until Monday.

Whitt said firefighters now hope to have the blaze under control within 24 to 48 hours.

Officials are trying to head off a potentially catastrophic failure of the 29,000-gallon tank caused by a buildup of heat, which would lead to an explosion Whitt described as like "a small thermal nuclear bomb" producing a fireball several hundred yards wide. An explosion also could throw metal shards up to a mile away. Officials ordered mandatory evacuations within a one-mile radius.

Whitt said firefighters have been successful in keeping the tanker cool since it caught fire Tuesday, but worried that it was showing signs of melting.

"Quite frankly, we are very lucky," he said. "We were really able to put a dent in the progression of the fire."

It was unclear how the tanker caught fire. It was burning at the Northern Propane Energy yard in Lincoln, about 30 miles northeast of the state capital in Northern California. It was surrounded by trucks, other rail cars and storage tanks containing at least 170,000 gallons of additional propane that Whitt said are "at risk" as the fire burned. A gas pipeline also runs through the area.

One worker at the rail yard was injured in the initial fire and suffered flash burns, but has been released from the hospital.

The procedure to drain the rail car of propane, called a "hot tap," will begin later in the day. The tanker will remain in place as a crew cuts the outer layer of the tanker and welds a pipe to the side. Steam will then be pushed inside, forcing out the propane and funneling it into a freshly dug basin, where it will be ignited and allowed to burn itself out. The burning process is expected to take up to eight hours and produce black smoke.

"We hope by the time you wake up in the morning that the entire situation will be resolved," said Jeff Carman, assistant chief for the fire department in nearby Roseville.

That would be welcome news to the thousands of residents forced to flee their homes. The American Red Cross said 270 people have taken shelter in three evacuation centers.

Roza Calderon, who lives with her family about a block away from the propane yard where the tanker was burning, described flames as high as utility lines before she evacuated.

"It was a big flame. It was getting worse," she said.

The 26-year-old accountant said she was staying with her husband, daughter and mother at a hotel in Sacramento.

At one center, the Kilaga Springs Lodge at a nearby Sun City community, volunteers set out 20 cots but had to add more as evacuees streamed in through the night.

One evacuee at the center, 21-year-old Richard Reyes, said he was hoping to be allowed back to his house soon but was concerned about the potential danger.

"I guess we began to realize the situation was rapidly deteriorating when they had to call in a team from Texas. They called them super firefighters who fight petroleum fires," said the student and part-time mechanic. "We were under the impression that they were going to let the propane burn out, like in a BBQ pit."

Highway 65, a major commuter thoroughfare between Sacramento and Lincoln, remained closed near the blaze. Authorities didn’t know when that section would reopen.

___

Associated Press writer Sheila V Kumar contributed to this report from Sacramento.