The sinking of a Spanish trawler that killed 21 crew members off Canada in 2022 was caused by overloading, poor safety protocols, lack of maintenance and errors by the captain, according to an official report.

The Villa de Pitanxo, based in the Spanish port of Marin, sank some 450 kilometres (280 miles) off the eastern coast of Canada in February 2022 with 24 crew on board.

Only three survived, including the captain, who, along with the vessel's owner, is under investigation for involuntary manslaughter.

A probe by a Spanish transport ministry agency charged with investigating maritime accidents found the ship had exceeded its authorised crew and was carrying excess equipment and fuel tanks, according to a copy of its findings seen Thursday by AFP.

Water entered through improperly sealed drainage conduits, and crews were unaware of the risk of leaving them open, it added.

"Crew members did not appear to understand the importance of closing watertight openings below the main deck," the report said. 

Flooding compromised stability and caused engine failure.

The report also cited poor captain decisions, inadequate crew training, outdated survival suits, and life rafts that failed to deploy. 

Nine bodies were recovered, and 12 remain missing in near-freezing waters.

A Canadian rescue mission was launched at the time, but rough seas and fierce winds complicated the search for survivors.