The nude body of a man was found at SeaWorld Orlando on Tuesday lying across the back of an 11,000-pound killer whale that was moved to Florida after it was involved in the death of a trainer.

Police were still trying to contact relatives of the 27-year-old Miami victim, whose name was not disclosed.

One expert said the 22-foot whale named Tillikum, the largest killer whale in captivity, could have mistaken the man for a toy.

"Killer whales play," said Sam Gruber, a marine animal expert at the University of Miami. "They are often seen tossing prey around for no apparent reason other than play."

Investigators said the victim apparently hid in the park after it closed, took off his clothes, then climbed a fence outside the gigantic breeding tank and jumped into 55-degree water with Tillikum, whose name means "Friend" in the Chinook language.

A park employee spotted the man's body draped over the back of Tillikum about 7:35 a.m. Tuesday in one of the whale pools behind Shamu Stadium, said Victor Abbey, SeaWorld's executive vice president and general manager. The man's swimming suit was found in the tank.

"It's been a pretty bizarre day," said Jim Solomons, a spokesman for the Orange County Sheriff's Office. "No one has come forward and said, 'John or Bill or Mike hasn't come home from SeaWorld.' It all just adds to the mystique."

Animal-rights groups, including the Humane Society of the United States, said the death shows why whales should not be held in captivity.

"The fact that a SeaWorld patron was able to gain access to the whale pools after the park was closed demonstrates that SeaWorld does not provide enough security for whales and visitors alike," said Naomi Rose, a marine mammal scientist for the Humane Society of the United States.

"SeaWorld and all marine parks should have security officers posted around the whale pools while the park is closed to prevent this kind of tragedy," Rose said.

Russ Rector of Fort Lauderdale, president of the Dolphin Freedom Foundation, said, "This animal is demented. Keeping those animals in small concrete boxes and making them do stupid animal tricks makes them angry and dangerous."

Abbey said three security officers patrol the Shamu Station area overnight, although no one is specifically stationed at the tank that holds Tillikum, the attraction's only male orca of breeding age.

The park, which has no surveillance camera at the breeding tank, will review its security measures, Abbey said, adding that "In the 35-year history of SeaWorld, this has never happened before."

SeaWorld maintains that its displays educate millions of people and boost efforts at conservation.

The U.S. Department of Agriculture, which regulates wild animals in captivity, also will examine safety precautions at SeaWorld.

"If it appears there is any negligence on the part of SeaWorld causing or contributing to the situation by not having a reasonable barrier to exclude the uninvited public, we will investigate further," said Ron DeHaven, a Department of Agriculture spokesperson.

Tillikum was brought to Orlando to breed. And as long as the park is successful at captive breeding, it doesn't have to attempt controversial captures in the wild.

Federal officials had previously expressed concerns that Tillikum could kill again.

Tillikum, who has fathered four calves, is not trained to interact with humans but is sometimes used in shows to splash water on park guests, Abbey said.

In granting a permit to transfer Tillikum to the attraction, National Marine Fisheries Service officers said they were hesistant to do so because they didn't want to see the "tragic incident" in Canada repeated in Orlando.

Tillikum and two female whales drowned their trainer in front of spectators at Sealand of the Pacific in British Columbia in 1991. The park closed its whale habitat because of the accident that killed Keltie Byrne. Officials said Byrne accidentally slipped and fell into the water. The whales drowned her by not letting her surface for air.

No one knows why the Miami man jumped into the whale tank. A preliminary examination of the man's body found no bite marks or other wounds, and the cause of death appears to have been by drowning or hypothermia in the chilly water, investigators said.

Since the body was found on Tillikum's back, it's unlikely the whale was behaving aggressively, Rose said. The whale was probably playing with the man and continued to play with the body after the man died, she said.

Heidi Harley, a marine mammal psychologist at the University of South Florida, said killer whales have been known to hold humans underwater.

"You could have a bored animal that wants to play, but generally an animal that's had experience with humans has a sense of their limitations," she said.

If the whale did hold the man underwater and drown him, Harley said that would probably be aggressive behavior.

She said she was surprised to learn that the body was found on the whale's back, speculating that the giant sea animal could have been trying to lift the man to safety.

"It sounds like he picked him up," she said. "That's not necessarily an aggressive thing. It's possible he picked him up if he was in trouble."

Brad Andrews, a biologist for SeaWorld, said he couldn't speculate on why the body was found on Tillikum's back, but he said he agreed that it was not an indicator of aggressive behavior.

The 14-year-old Tillikum was captured in the frigid waters off Iceland.

Tuesday morning's Shamu show was canceled while investigators removed the man's body at about 11:30. The Shamu show resumed at 2 p.m.

Customers at the park were not told about the fatal accident.

"I didn't hear about it," said Becky Larsen, a White Springs science teacher who was leaving the park after taking her infant son to feed dolphins. "I'm sorry he had to lose his life, but it's absolutely ludicrous."