HARTFORD, Conn. (AP) A federal investigation into the death of a Hartford firefighter during a house blaze last October has found that a low-air alarm on his breathing tank failed a test after the fire, but Hartford officials say the alarm activated.

A medical examiner concluded 48-year-old Kevin Bell died because his tank ran out of air. He was the first Hartford firefighter to die in the line of duty in four decades.

The National Institute for Occupational Safety and Health inspected Bell's air tank after his death. One report in its ongoing investigation says an alarm that would have sounded when the air level got down to about a quarter tank failed a test.

Hartford Fire Chief Carlos Huertas says the alarm activated during the fire and firefighters' tanks are checked regularly.