Exactly what triggered the explosion was being investigated, and Hohman said firefighters were informing residents of about 70 nearby homes that they could leave if they choose and shelter will be provided. However, no one was being forced to evacuate.
Derailments have done great damage before in Baltimore, a city with countless train tracks. Twelve years ago was the derailment and chemical fire in Baltimore's Howard Street tunnel. Rail cars burned for five days underground in July 2001. Portions of downtown were closed and rail traffic across the U.S. was affected for days. CSX eventually agreed to pay Baltimore $2 million to help defray the city's cleanup costs.
The National Transportation Safety Board and the Federal Railroad Administration were sending teams to investigate Tuesday's crash.
Photos showed at least a dozen train cars off the tracks, including at least one tanker car. Sease said four of the cars believed derailed carried terephthalic acid, which is used in the production of plastics and polyester, among other things. He said it is not listed as a hazardous material.
One of the cars still burning was carrying terephthalic acid, and another was carrying fluoroacetic acid, Hohman said. Fluoroacetic acid can be used as a pesticide.
Hazardous materials moving through Baltimore and elsewhere in Maryland was the subject of an agreement a few years ago between the state and CSX. After a November 2007 derailment involving a freight train carrying hazardous materials near Camden Yards, CSX agreed to give security officials real-time information about potential harmful cargo moving through the state on freight trains. Railroads had previously guarded such details as proprietary information.
Also hit by a serious derailment this month was Bridgeport, Conn. On May 17, more than 70 people were injured when a commuter train went off the tracks. The eastbound train from New York City derailed during evening rush hour, came to a stop and was struck about 20 seconds later by a westbound train.
In Rockview, Mo., on Saturday, a cargo train crash injured seven people and destroyed a highway overpass that could take a year to repair.
Despite the high-profile railroad accidents, the overall number of such crashes has been declining industry wide and for CSX over the past decade.
Last year was the safest year on record for the railroad industry, according to the railroad administration. All train accidents are down 43 percent since 2003, and derailments are down 40 percent over the same period, according to data provided by the administration. Freight train derailments specifically are also down 40 percent.
In each of the past five years, CSX has reported more than 100 deaths in accidents and incidents involving the railroad.
CSX, based in Jacksonville, Fla., operates over 21,000 miles of track in 23 eastern states and two Canadian provinces.
Its shares traded higher Tuesday before the derailment was reported. The shares closed down 20 cents at $25.30.
Bertha Pressley and her husband Tom Brown said their townhome in Middle River, about 3 miles away, shook and they initially feared a bomb or natural disaster.
"I thought it was terrorism," Pressley said.