A Red Line train derailed yesterday at Alewife Station, but no injuries were reported, MBTA officials said. The fourth car of a six-car train went off the track just south of the station, said T spokesman Joe Pesaturo. Sixty-five passengers were safely evacuated. Buses were being used to replace Red Line service between Alewife and Harvard in both directions, Pesaturo said in an e-mail, until the car could be put back on the rails and moved. He said it is uncertain whether train service will return to normal today and he recommended passengers check www.mbta.com. The train had just left Alewife and was one train-length out of the station. A full investigation was underway, Pesaturo said. A critical independent review of the MBTA, released last month, cited hundreds of millions of dollars in unfunded safety projects that the T has not been able to afford. The report singled out an $80 million unfunded project between Harvard and Alewife stations to replace a system of floating concrete slabs beneath the track, as well as to repair leaks. Without those repairs, the Red Line risks derailment, according to internal MBTA documents. Pesaturo said that the investigation into yesterday's derailment is not related to the track issue and that investigators were focused on the vehicle, not the track bed. The T has had several equipment problems in recent days. A Green Line train derailment near Copley Square on Dec. 13 caused no injuries, but led to a service suspension for several hours. Repairs to a 40-foot wall panel on the Red Line at the Porter Square station, which is in danger of coming loose after water leaks, caused rush-hour delays on the line Monday. 'I think we said it before: It's the whole challenge of dealing with an aging system,' said Jeffrey B. Mullan, state transportation secretary. Mullan said that passengers should not feel at risk and that crews monitor the subway system constantly. Yesterday's derailment was probably related to a wheel problem on the fourth car of the train, Mullan said. Noah Bierman can be reached at nbierman@globe.com. 