Disaster struck on Thursday as a freight train collided with a passenger train in Washington County, Arkansas. The accident has left dozens injured and has prompted an investigation by the National Transportation Safety Board (NTSB).

According to a report from Little Rock NBC affiliate KARK, five people were critically injured in the crash and at least 20 more were injured in some way. There were reportedly 44 people on-board the passenger train at the time of the crash. Several of those injured were reported to have been train crew members.

The NTSB announced yesterday that it has launched an investigation into the incident. An NTSB “go-team” of railroad investigators has been sent to the site of the crash. The team is expected to be at the scene of the accident for five to seven days to collect perishable evidence.

The KARK report quotes police as stating the passenger train left Springdale, Arkansas early Thursday morning and later slipped off its tracks. The freight train was reportedly sent for aid, but ended up crashing into the passenger train.

According to the NTSB the passenger train, made up of one locomotive and four cars, stalled in what is called “dark territory” – a section of track controlled by a railroad’s operations control center rather than signals. The cause of the stall has not yet been determined.

An NTSB spokesperson went on to state that the rescue train dispatched to help collided head-on with the passenger train’s lead engine. Both trains were derailed as a result of the crash, though no fuel was released and there were no fires. Both of the trains had forward-facing video recorders that should help investigators determine the cause of the accident. The official number of passengers injured in the crash has not yet been determined.

The next NTSB media briefing has been scheduled for Friday at 5 pm EDT in Springdale.