The MBTA's Green Line Extension is back in operation after a derailment Tuesday afternoon sent several passengers to the hospital and caused another headache for a transit agency that can't seem to catch a break.

The MBTA said Wednesday it is not yet clear when regular service will resume on the Green Line as crews have not yet cleared a train that derailed in Cambridge.

State Rep. Mike Connolly expressed concern about the incident, saying “it could have been much more catastrophic.”