A transformer that exploded outside the Russell Senate Office Building on Monday night did not release a hazardous chemical, a spokeswoman for the Capitol Police said Tuesday.

“There were no hazardous materials found,” Jessica Gissubel said.

The scene was cleared before business hours Tuesday morning.

The transformer exploded about 10:40 p.m. under the corner of First and C streets Northeast. (The underground vault is exposed to the street by a grate.) Early reports suggested that the substance released from the fire might have been toxic, as the cooling oil used in older transformers often contain PCBs, a carcinogen.

About a dozen Capitol Hill employees, mostly police officers, were treated by the District’s hazardous materials team, according to a D.C. Fire Department spokesman.

“They took them through the decontamination process as a matter of precaution,” Alan Etter said, adding that they were treated from the knees down. “They didn’t breathe anything in, nobody had to go to hospital.”

Gissubel explained that the nature of the incident dictated that the D.C. Fire Department and its HAZMAT team respond. “It was an industrial accident” on the street, she said, adding that “If it were inside the building [our HAZMAT team] would have absolutely responded.”

— Suzanne Nelson