A two week examination of the charred wreckage of the scuba diving boat Conception has been inconclusive, leaving unanswered what caused the tragedy.

Pieces of the boat have been sent to labs for additional testing, the Associated Press reported.

The boat went down in flames early on Sept. 2 just off Santa Cruz Island, as its captain made a chilling distress call, telling a Coast Guard operator he was “On board a vessel on fire.”

The captain and four crew members were all asleep on the upper deck when the fire broke out, contrary to Coast Guard rules requiring a crew member to conduct a “roving” night watch at all times.

The probe into what caused the fire — conducted by the US attorney’s office in Los Angeles, the Coast Guard and the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives — is expected to last a year.

The fire claimed the lives of 33 passengers and one crew member; the dead ranged in age from 16 to 62.

All that was left of the 79-foot boat was a charred hull.