January 2, 1973: Electrical arc causes a fire on a Bluebird between Broadway and South Station. Three MBTA employees lift all 200 passenger from the train to the tunnel; they then take refuge in a stalled Silverbird further down the tunnel. No serious injuries of deaths, but firefighting was delayed by the need to drag hoses for half a mile through the tunnel.
February 6, 1973: Another electrical fire on a Bluebird near South Station. One dead of smoke inhalation - 74-year-old Arthur Rotch of Milton - and 94 hospitalized.
The fires were believed to be caused by faulty third rail shoes on the Bluebird (the 1963-built 01400 series cars). After the two incidents, the MBTA made a number of improvements. Cab radios were added to the Bluebirds (the first fire was only reported to dispatch when passengers on foot reached the Silverbird), water mains and emergency telephones installed in the tunnels, emergency exits tested and clearly marked, etc.
I can send you some old scanned Globe articles - PM me with your email address if you want them - but they're still under copyright so I cannot post them here.