SANTA CLARA, Calif. -- There was some sad news Saturday out of the Marine Mammal Center in Sausalito, a wayward sea lion that was rescued from a Santa Clara creek is suffering from a fatal disease and will have to be euthanized, officials said.

The sea lion, named "San Tomas" after the expressway near where she was found, underwent an electroencephalography on July 10 to see if the animal was suffering from the poisoning, which comes from exposure to harmful algal blooms in the water.

Jim Oswald, the communications director at the Marine Mammal Center where the animal was being tested, said that the center did not find immediate proof of the poisoning, but sent the test results to other animal specialists that found direct indication of chronic poisoning.

"She has been suffering from it for a long period of time," Oswald said. "We don't know how long, but it was enough to damage the brain."

Oswald said that the poisoning most likely occurred when the sea lion ate fish that had consumed the algal blooms, and may have caused it to lose its way and enter the aqueduct where it was trapped for more than a week.

"It's a possible reason," Oswald said. "One of the effects of long-term exposure is that it can cause animals to get disoriented."

Oswald said that the center has observed an increase in the harmful algal blooms since the first diagnosed case in 1998.

The sea lion is scheduled to be euthanized in three or four days.

"Every little bit of information (scientists) gain helps them learn more about domoic acid poisoning, and through the death of San Tomas, we'll be able to have a better understanding of the poisoning and the effects on animals," said Oswald.