Honolulu firefighters returned Saturday to a fire that rekindled in a pile of junked automobiles at a recycling yard in Campbell Industrial Park.

Honolulu Fire Department spokesman Capt. Kevin Mokulehua said 12 firefighters returned to the Schnitzer Steel Hawaii Corp. property on Hanua Street and brought the flames under control by 12:30 p.m.

The fire had started about 5:15 p.m. Friday and caused heavy smoke and flames to erupt from a pile of cars about 40 feet high and 30 feet by 30 feet in area.

About 35 firefighters responded and crews battled the blaze until about 2:30 a.m. Saturday.

Mokulehua said firefighters returned just before 9:30 a.m. after a battalion chief went to reassess the situation and noticed pockets of smoke coming up from the pile.

He said Schnitzer employees assisted by breaking up the scrap pile with heavy equipment, giving firefighters access to smoldering portions.

During Saturday’s operation, smoke was seen rising from the concrete slabs that the junk pile was sitting on and pooling water on the ground appeared to boil, Mokulehua said.

Firefighters also notified the Coast Guard about the potential environmental impact because water from the fire operation could enter an adjacent canal that leads to the ocean.

Carroll Cox, who runs the nonprofit EnviroWatch, said he was at the property Friday to investigate any effects on the environment from the fire.

He said plant supervisors invited him onto the property to show him there were no violations, and he saw the fire in a crowded area with several people using heavy equipment to separate trash for firefighters.

“They were aggressively going at it,” he said. He couldn’t see any runoff from the firefighting operation going into the adjacent canal and found no major issues, he added.

Cox noted a higher risk for fires at recycling businesses because of the fuels and fumes in the rubbish.

The property has been the site of at least five fires since 2000. One that burned a pile of driftnets in January 2009 was determined to be intentionally set.

The environmental concerns come as Schnitzer Steel continues its legal battle with competitor Island Recycling, accusing it of violating environmental laws.

Earlier this year, Schnitzer Steel obtained a court order allowing it to test soils in the drainage canal on the Island Recycling property on Kaomi Loop in Campbell Industrial Park.

Tests done by Schnitzer’s consultant showed lead levels in the drainage ditch that are 85 times higher than “environmental action levels” established by the Department of Health and mercury levels 40 times higher than the action level, according to court documents.

However, the state Health Department says in court filings in the case that most of the metals are within the allowable level for an industrial park. The department said there is no water in the ditch, and there have been no discharges into the ocean.

Island Recycling accused Schnitzer of trying to shut down its main competitor.

Firefighters estimated this weekend’s fire caused $1,000 damage to the contents, while the cause remained undetermined.