Mechanical failure has been crossed off the list of possible causes of last Thursday's fatal military helicopter crash off the coast of Nova Scotia.


Investigators are now looking at human error and environmental factors as more likely causes, Air Force spokesperson Major Kevin Toone said.


The CH-149 Cormorant helicopter crashed into the Atlantic while performing a nighttime training exercise with a Canadian Coast Guard crew on July 13.


Three Search and Rescue Technicians died in the crash.


One of the victims of the crash, Sergeant Duane Brazil, was laid to rest Thursday during a full military funeral in St. John's, NL.


Immediately after the crash, critics pointed to the tail of the aircraft as a likely cause of the crash.


However, Toone said the aircraft was working properly before it pitched into the water near Canso.


Witnesses on the deck of the Coast Guard vessel that was taking part in the joint-training exercise described seeing the helicopter suddenly lurch to one side, then crash nose-first into the water.


In 2004, concerns about cracks in the hub of the tail rotors forced the military to restrict training flights to only three hours. The restrictions were put in place shortly after the fleet was declared ready to fly.


Military officials have not said how long the Cormorant was in the air prior to Thursday's fatal crash.


However, Toone said investigators have virtually eliminated the tail rotor issue as a factor in the crash.


In addition to Brazil, 39, the crash also killed Master-Cpl. Kirk Bradley Noel, 33, and Cpl. Trevor Sterling McDavid, 31.


Brazil's brother, Gary, died when a Coast Guard helicopter went down in 2000 off the coast of Newfoundland.


Thursday's crash also injured Capt. Gabriel Simon Ringuette, 41, Sgt. Martin Francis Moloney, 48, Capt. Ronald Earl Busch, 40, and Major Gordon Clements Ireland, 42.


Investigators are continuing to comb through the wreckage to determine the cause of the Thursday's crash.