Authorities said six people were killed and at least five others were injured after a commuter bus and a school bus collided in southwest Baltimore in what authorities are calling a “significant wreck.”

No schoolchildren were onboard the school bus, Baltimore police said, but the bus was thought to be on its way to pick up a student. The crash happened about 7 a.m. near Frederick and Monastery avenues.

Authorities had initially said at least three people were killed but noted that it was a “fluid situation.” They later updated the number of fatalities to six. Police said the driver of the school bus was among those who were killed. The names of the victims were not released, pending notification of relatives.

A spokesman for the University of Maryland Medical Center said it had received five patients at the shock-trauma division and at the its emergency room. Of those five, one is in critical condition, and four are in fair condition, according to Michael Schwartzberg, the spokesman for the facility.

Pictures from the scene showed two mangled buses and debris in the roadway. In a briefing, police spokesman T.J. Smith said it “looked like a bomb” had exploded at the crash scene.

Authorities said drivers should expect the roadway to be closed for a while.

At a briefing near the site, police said their initial investigation showed the crash happened about 7 a.m. in the 3800 block of Frederick Avenue. The school bus was headed east on the road when it struck a gray Ford Mustang. The school bus then hit a pillar at a nearby cemetery and continued eastbound and collided with an MTA commuter bus. It hit the driver’s side of the commuter bus.

The school bus is thought to have been headed to pick up a child about four or five blocks from the scene, police said. It was not known where the child was headed. It was also not clear whether the school bus was working for the city’s school system or another system. Officials with Baltimore City schools did not immediately respond to a request for comment.

Authorities said five of those killed were onboard the MTA bus. The driver of the school bus was also killed. An aide on the school bus was taken to a hospital, but the person’s condition was not released. The driver of the Mustang also was taken to a hospital in an unknown condition.

Officials cautioned that while there were six fatalities, that “number could change,” Smith said.

“It’s a pretty horrific scene,” Smith said.

Baltimore City Police Commissioner Kevin Davis said at the briefing, “Our thoughts and prayers go out to the victims and their families.”

“The folks on the bus were working folks,” Davis said. “They were on their way to make a living. They were on their way to support their families.”

Authorities said their investigation into the deadly crash was still preliminary, and they described the crash scene as being complicated because it involved several vehicles.

Maryland Gov. Larry Hogan (R) described the crash in a statement as “horrific” and gave his condolences to the victims and their families.

“We will continue to pray for those who were injured, as well as the first responders who worked swiftly and continue to care for the injured,” he said.