The buses will run between North Station and Medford/Tufts and Union Square in Somerville, the MBTA said in a post on social media early Wednesday morning.

After a Green Line derailment near Lechmere station in Cambridge sent seven people to the hospital Tuesday, the MBTA moved to replace the line with shuttles as federal and state investigations examine the cause of the incident.

The MBTA is currently investigating how “human factors,” including the train operator’s action, could have been involved with the incident.