LOS ANGELES ? Former dolphin trainer-turned-activist Ric O'Barry called Friday for a federal investigation into this week's deadly killer whale attack at SeaWorld Orlando.

O'Barry, who used to train the dolphins which performed in the 1960s US television series "Flipper," accused SeaWorld managers of ignoring clear warning signs concerning Tilikum, the orca involved in Wednesday's attack.

The whale ? which grabbed trainer Dawn Brancheau and dragged her under the water to her death ? has been linked to two previous fatalities while in captivity.

O'Barry, who features in the Oscar-nominated documentary "The Cove" about dolphin hunting in Japan, said the attack was the result of a "calculated risk on the part of a $1billion captive dolphin and whale industry."

"SeaWorld allowed public and trainer contact with an orca that was a known risk, and after three deaths they're suggesting that it actually continue," O'Barry said in a statement with Dave Phillips of the Earth Island Institute.

"We believe this situation warrants the immediate initiation of a federal investigation into SeaWorld's possible negligence and violations of the Marine Mammal Protection Act," O'Barry and Phillips added.

"Along with sadness of this tragic event we can't help feeling anger toward those who insist upon exhibiting these wild creatures in habitats that can drive them to violence."

O'Barry has been an ardent campaigner against marine parks such as SeaWorld since the 1970s, saying his views on an industry he helped create changed after one of the dolphins he trained for "Flipper" died in his arms.