Five people were sent to the hospital after a Green Line train collided with another train early Sunday morning, bringing in federal investigators to examine the crash.

According to the MBTA, just before 12:30 a.m. a train carrying five passengers struck a stationary out-of-service train parked at East Somerville Station.

As a result, “one car on each of the two-car trains derailed” and one passenger suffered a neck injury that required medical transport. Four Green Line operators were also sent for medical care, but were “conscious and alert,” according to the MBTA.

An investigation into the collision will be led by the National Transportation Safety Board, which announced via social media that it would dispatch a team to the Bay State on Sunday.

“NTSB is sending a team to investigate Sunday’s train collision involving a MBTA light rail passenger train and a standing out of service train near Somerville, Massachusetts. Team expected to arrive today,” they wrote.

According to the MBTA, shuttle buses replaced service between Medford/Tufts and North Station “while personnel continue to investigate an accident at East Somerville last night.”

This is a developing story.