By Ian Simpson
(Reuters) - A Baltimore school bus with no students aboard smashed into an oncoming commuter bus on Tuesday, killing at least six people and injuring 10, as police hoped an autopsy of the school bus driver would shed light on the cause of the accident.
The yellow school bus hit a wall, rear-ended a Ford Mustang and struck a pillar before veering across a boulevard's center line into the Maryland Transit Administration bus, police spokesman T.J. Smith told a news conference.
The impact tore off most of the driver's side of the commuter bus. Among the injured, two were hurt critically in the morning rush-hour crash, and rescuers had to cut bus seats out to reach victims, Smith said. The injured included the car's driver and a school bus aide.
"It literally looks like a bomb exploded in the bus," Smith said at the crash scene in southwest Baltimore.
There were no skid marks, and the 67-year-old male school bus driver died at the scene. Smith said an autopsy would determine if he had a medical condition that kept him from slowing the bus.
Five people on the commuter bus also died at the site, including its 33-year-old female driver. Police said the accident scene extended over several hundred yards.
Investigators pulled some vehicle recording devices from the wreckage, possibly including video camera footage, Smith said.
The National Transportation Safety Board sent an eight-person investigative team to the crash site, with more personnel on the way, lead investigator Jennifer Morrison told reporters.
The Baltimore City Public Schools said the bus was contracted from AA Affordable Transportation of Baltimore. It was used to transport 18 elementary school students who need specialized services, such as homeless children or non-English speakers, it said in a statement.
Smith said the school bus was on its way to pick up a student with the driver and the aide aboard. Thirteen people were on the transit bus.
(Reporting by Ian Simpson in Washington; Additional reporting by Gina Cherelus in New York; Editing by Alistair Bell and Peter Cooney)