Officials in Florida say a veteran 40-year-old trainer at SeaWorld was killed by a whale when she slipped and fell in its tank.

SeaWorld Orlando President Dan Brown says officials are investigating but it appears to be an accident.

He says the trainer was one of the park's most experienced.

Spectator Victoria Biniak told WKMG-TV that the trainer had just finished explaining to the audience a show they were about to see Wednesday when the whale appeared to grab the trainer and thrash her around.

Brown says SeaWorld has never experienced an incident like this.

"She was rubbing the killer whale's head, and (it) grabbed her and pulled her in" to the pool, said Chuck Tompkins, Corporate Curator of Zoological Operations at SeaWorld Parks & Entertainment.

Forty-year-old Dawn Brancheau, a trainer with 16 years experience at SeaWorld, was dead when rescue officials arrived, said Orange County Sheriff's spokesman Jim Solomons.

Media reports said the orca at the park's Shamu Stadium grabbed the woman by the waist, thrashed her about and took her underwater.

The trainer was killed just before the start of a public performance and the stadium was immediately evacuated.

Dan Brown, president of SeaWorld Orlando, said the victim was one of the park's most experienced animal trainers, and that she drowned.

There were initially conflicting reports about how the incident occurred. The Orlando Sentinel quoted a spectator as saying the whale came up from the water and grabbed the trainer by her waist. The sheriff's official said preliminary accounts indicated she slipped and fell in, but that was still under investigation.

"We don't know what was going through the killer whale's head. It just got done doing a wonderful session with Dawn ... his behaviour was great ... that's the reason that she was rubbing his head," Tompkins told Reuters.

"We don't have any other specifics yet. This is a terrible, terrible situation that's happened, it's a tragedy, our greatest sympathy goes out to her family."

The Florida park is owned by the Blackstone Group, a private equity company that also owns part of the Universal Orlando theme park.

A spokesman for SeaWorld in San Diego said killer whale shows had been suspended following the death in Orlando.

"We cancelled the show this afternoon in light of the incident in Orlando. We'll look at it again tomorrow," said SeaWorld spokesman David Koontz. "We're very saddened by the loss of a sea world family member."

According to the Orlando Sentinel the orca involved in the incident, named Tillikum but popularly known as "Tilly," has a controversial past.

CRITICISM FROM PETA

The whale was blamed for the drowning of one of his trainers in 1991 while he was performing at Sealand of the Pacific in British Columbia, the newspaper said.

Sold to SeaWorld as a stud in 1992, the whale was involved in a second incident when authorities discovered the body of a naked man lying across his back in July 1999.

Authorities said the man, who had either snuck into SeaWorld after hours or hidden in the park until it closed, most likely drowned after suffering hypothermia in the 55-degree water.

A former contractor with SeaWorld told the Sentinel that Tillikum is usually kept isolated from SeaWorld's other killer whales and that trainers were not allowed to get in the water with him because of his violent history.

Animal rights advocacy group People for the Ethical Treatment of Animals slammed the death as "a tragedy that didn't have to happen."

"For years, PETA has been calling on SeaWorld to stop confining oceangoing mammals to an area that to them is like the size of a bathtub," the group said in a statement.

"It's not surprising when these huge, smart animals lash out."