Joe Steffen, 51, died because of an air embolism, an autopsy has found. ((CBC))

An American diver who died whileexploring a flooded Newfoundland mine suffered an air embolism, an autopsy has determined.

Joe Steffen, 51, was found Sunday afternoon near the ceiling of one of the flooded tunnels in the abandoned iron ore mine in Bell Island, about 35 kilometres west of St. John's.

Members of Steffen's dive team attempted to revive him but failed.

In diving, an air embolism can occur when a diver ascends too quickly, and gas bubbles enter the bloodstream. An embolism can become fatal, for instance, if a bubble rests in the heart.

Steffen was a member of an international team of divers who had been invited to explore the No. 2 mine at Bell Island by Ocean Quest Adventures, which is hoping to develop the site as an adventure tourism attraction.

The team resumed its exploration on Monday.

Production at the No. 2 mine ended in 1949. The rest of the Bell Island mine, which has been flooded since, closed in 1966.