A freight train derailed in the Rosedale section of Baltimore County about 2 p.m. Tuesday, causing several cars to catch fire and sending thick plumes of white and black smoke into the sky.
Up to 15 cars derailed, and flames were visible from the wreckage. Two cars remain on fire. Many more cars remain upright.
WBAL-TV reported an explosion occurred, and Baltimore County police confirmed HAZMAT crews responded.
Firefighters are using hand-held sensors to detect hazardous materials, News4's Jackie Bensen reported.
Firefighters evacuated the immediate area.
Pulaski Highway, which runs parallel to the tracks about a block away, is closed between Chesaco Avenue and the Baltimore city line, police said. Some side streets also are shut down.
The air is thick with smoke, WBAL's Kate Amara reported. Pedestrians are covering their mouths and noses with their shirts.
A truck may have been involved, WBAL reported, though it is unclear how. A truck is visible in the wreckage, and there is a crossing near the site of the derailment.
Several nearby buildings collapsed, police said. The side of a large building next to the tracks appears to be blown off.
Dan Cook, who works nearby on 68th Street, told WBAL the blast blew some metal signs off his building. "It was a pretty big explosion," he said.
The derailment occurred in the area of Lake Drive and 66th Street, about a mile east of Interstate 95.
Amtrak told NBC News the derailment and fire in Baltimore does not affect their service. The derailed train is on CSX tracks not near Amtrak tracks.
The Maryland Transit Administration is anticipating delays on MARC's Camden Line because of freight trains stacking up because of the incident, according to transportation reporter Adam Tuss.
The National Transportation Safety Board is monitoring the derailment and fire.
Less than a year ago, a CSX derailment killed two college students in Ellicott City, Md. According to an NTSB report, 21 of the train's 80 cars derailed, including six that fell into a public parking area below the elevated track. The cars spilled coal throughout the area, crushing and suffocating two young women who had been sitting on a railroad bridge near the train tracks. The cause of that derailment remains under investigation.
Check back here for more as this story develops.