The US federal job safety agency fined SeaWorld Orlando 75,000 US dollars for three violations uncovered while investigating the February death of a trainer who was grabbed by a killer whale and dragged underwater.

The Occupational Safety and Health Administration categorised the most serious violation as "wilful", or showing indifference or intentional disregard for employee safety.

That citation, carrying a 70,000 US dollar penalty, was for exposing workers to drowning hazards when interacting with killer whales.

The agency proposes not allowing trainers to have any physical contact with Tilikum, the killer whale responsible for trainer Dawn Brancheau's death in February, unless protected by a physical barrier.

The Osha report described Tilikum as having "known aggressive tendencies".

The six-ton whale was one of three orcas blamed for killing a trainer in 1991 after the woman lost her balance and fell in the pool at Sealand of the Pacific near Victoria, British Columbia.

Tilikum also was also involved in a 1999 death, when the body of a man who sneaked by SeaWorld Orlando security was found draped over him.

Sea World trainers were forbidden from getting in the water with Tilikum because of the previous deaths. But the killer whale still managed to grab Ms Brancheau's long hair as she laid on her stomach on a cement slab in three inches of water. The cause of death was drowning and traumatic injuries.