A commuter train carrying 35 passengers derailed about a quarter mile past the Belmont Center Commuter Rail station around 9 a.m. this morning.
MBTA Transit Police said the passengers were removed from the train, and boarded an MBTA bus. They also said the Transit Police Accident Reconstruction Unit assessed the circumstances of the derailment.
The train was heading outbound to South Acton when it happened, and it had left North Station at 8:12 a.m., transit police said.
While the cause was not immediately clear, transit police said there is "nothing suspicious" and that the investigation is being investigated by the Massachusetts Bay Commuter Railroad Company.
"The train derailed at a very low rate of speed when four wheels on the first coach behind the locomotive slipped of the track just past the Belmont Center Commuter Rail stop," said Tom Halkin, a spokesman for the MBCR.
Halkin said crews are looking at the track and undercarriage of the train as possible causes.