ORLANDO, Fla. — A SeaWorld Orlando animal trainer was killed Wednesday afternoon during an accident at SeaWorld’s Shamu Stadium, park and law enforcement officials said.

Law-enforcement sources said the victim was Dawn Brancheau, a 40-year-old with extensive training experience.

Park authorities said a trainer was in a whale holding area when she apparently slipped or fell into the tank and was fatally injured by a killer whale.

Authorities provided few immediate details, but two witnesses told The Orlando Sentinel that one of the park’s whales had the woman by the upper arm, tossing her around in its mouth as it swam rapidly around and around in the tank.

Brazilian tourist Joao Lucio DeCosta Sobrinho, 28, and girlfriend Talita Oliveira, 20, were at an underwater viewing area when they suddenly saw a whale with someone in its mouth.

The couple said they watched the whale show at the park two days earlier and came back to take pictures. But Wednesday afternoon the whales appeared agitated before the incident occurred.

”It was terrible,” Sobrinho said.

The woman was bleeding, they said, and the whale turned her over and over as it swam.

Other eyewitnesses who were in the park for the Dining with Shamu program, which features a private buffet next to the killer whale habitat, told the Sentinel that a female trainer was petting a whale when it grabbed her and plunged back into the water with her. The whale reappeared on the other side of the tank.

SeaWorld President Dan Brown said in a brief statement, ”We’ve initiated an investigation to determine, to the extent possible, what occurred.”

Brown said no SeaWorld park had ever before experienced a similar incident and pledged a thorough review of all of the park’s operating procedures.

”Nothing is more important than the safety of our employees, guests and the animals entrusted to our care,” Brown said, his voice breaking slightly.

The whale used primarily for the Dining with Shamu program is named Tillikum, and that whale has been involved in other incidents at parks.

The large 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.

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 later concluded the man, who had either snuck into SeaWorld or hidden in the park until it closed, most likely drowned after suffering hypothermia. But they also said it appeared Tillikum had bit the man and tore off his swimming trunks, likely believing he was a toy to play with.

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

Animal-rights activists have long criticized SeaWorld and other marine parks for keeping orcas and other wildlife in captivity.