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.

Regular service has resumed on the MBTA’s Green Line following a derailment in Cambridge earlier this week that prompted a National Transportation Safety Board investigation, officials announced Thursday.