A fire suspected to be arson consumed a pile of railroad ties east of Longmont’s wastewater treatment plant Wednesday night, melting power lines and producing thick black smoke that could be seen from Firestone.

Police detained two young people seen running from the area, but no charges had been brought or arrests made as of 10:15 p.m. Officers could not yet say if the two were involved in the blaze, but said the fire did not appear to be accidental.

“We suspect it was started,” Police Sgt. Paul Campbell said, saying that detectives and an arson investigator had been sent to the scene.

Campbell said that city workers had been called to the plant as a precaution, but that the site was not believed to be in danger. He estimated the fire to be about a quarter-block in size.

The burning BNSF Railway ties were initially discovered by Officer Dave Kennedy, who reported the fire at 7:51 p.m. No one was injured in the blaze.

Police sealed off Martin Street west of the fire, between First and Third avenues, to keep the road clear for emergency vehicles and keep people back from the smoke, which was considered potentially toxic.

Most of the fire had been knocked down by 10:15 p.m. but Fire Services Chief Jerrod Vanlandingham said firefighters would likely spend all night putting out the last pieces of it.

“We’ll need to get a front-end loader and pull (the pile) apart,” he said. “This could be one that smolders for days.”

The downed lines knocked out several traffic lights, including the signal at Third Avenue and Pace Street and another at Third and Colo. 119. All signals were reported back on by 9:35 p.m.

Deb Cameron of Longmont Power and Communications said that about 300 LPC customers lost power during the fire, in an area between Martin Street to the west, Third Avneue to the north and Colo. 119 to the south.

Power was restored about an hour later, Cameron said, though a transformer near the wastewater plant was still out of commission and would not be abe to be repaired until after the fire was extinguished.

Power was also briefly knocked out to the wastewater plant itself, Vanlandingham said, but a secondary power source came on within mminutes.

No other structures were ignited by the fire, though more ties lay within reach of the flames. Not much was in the area, Vanlandingham said, except for trees, shrubs, railroad ties and debris.

“It’s just a bunch of smoke and nasty air quality,” he said.