SAN DIEGO -- Investigators are trying to find the cause of an oil spill that coated hundreds of birds with crude oil and may threaten other sea life, 10News reported.

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OILED BIRDS Mystery Spill Coats Birds In Crude Oil

Oil-slicked pelicans have been rushed to SeaWorld for treatment while teams of experts assess the damage.

Animal rescue groups are searching out and corralling birds coated with crude oil from what's now being dubbed the "Ventura Mystery Spill."

One official told 10News the birds lose their ability to keep themselves warm when they're oiled.

Smaller birds have been scooped off affected beaches and treated, while larger, endangered pelicans are now arriving at SeaWorld for emergency care.

Lauren Dubois, from SeaWorld, said, "When they have oil on their feathers they preen and don't take time to eat or drink, so they become emaciated."

SeaWorld staff members have been feeding the weakened birds fluids and juicy smelt for those ready for solid food.

"Once clean we dry them off, we leave them outside to get warmed up, fed and make sure they're stable so they can be released in the next few weeks," Dubois said.

The state is still trying to find the source of the oil spill. Once it finds the responsible party, the state will be sending a bill for cleanup and animal rescue efforts.

SeaWorld is one of 25 organizations statewide that participate in the Oiled Wildlife Care Network.