ROSARITO, Mexico (Border Report) — Seals, dolphins and sea lions are washing ashore lifeless in Northern Baja and no one knows why.

Pelicans are also dropping out of the sky and hundreds of dead mollusks have been found dead along beaches in recent weeks.

Investigators are trying to figure out if there’s a correlation, and whether bacteria in the water is responsible for the phenomenon.

Luis Figueroa, with the office of Mexico’s Environmental Protection Agency, says initially some of the animals were simply buried under five feet of sand, but the carcasses have been unearthed so they could do further tests on the remains.

A dead dolphin was discovered on the beach in Rosarito, Mexico about 20 miles south of the border. (Courtesy: Araceli Brown/Mayor City of Rosarito)

“We had to unearth them to perform biopsies and other exams,” said Figueroa. “We are taking the samples to the Autonomous University of Baja California in Ensenada where biologists will perform analysis and we are waiting for the results.”

Figueroa stated that dead sea life has been washing ashore as the levels of contamination in the ocean have gone up in recent months, but he stopped short of blaming it as the cause.

For months, a broken down treatment plant in the area has been sending millions of gallons of raw sewage daily into the ocean.

Dead pelican on the beach in Rosarito, Mexico. (Courtesy: Araceli Brown/Mayor of Rosarito, Mexico)

Beaches from the border south to Rosarito have been declared off-limits to swimmers as the bacteria levels in the water remain high and are considered a health hazard.

“From my point of view, I’ve been working along the coast for years, and it’s not common for animals to wash ashore dead,” said Figueroa. “You might get two or three in a week due to fishing efforts and the animals get tangled in nets, but not like this.”

Figueroa said except for a dolphin that beached itself after becoming sick, the others washed a shore already dead.

Araceli Brown, mayor of Rosarito, a beach community about 20 minutes south of the border went on social media and said there was a “presence of rare bacteria in the ocean.”

“I don’t see any mass contamination, if this was the case we’d see a ton of dead animals,” she said.

The exact number of dead sea life and birds has not been released.