SAN DIEGO (AP) — Marine scientists say they have found what they believe to be as many as 25,000 barrels that possibly contain DDT dumped off the Southern California coast near Catalina Island.

The sightings were made by researchers at the University of California San Diego’s Scripps Institution of Oceanography who mapped more than 36,000 acres of seafloor between Santa Catalina Island and the Los Angeles coast in a region previously found to contain high levels of the toxic chemical in sediments and in the ecosystem.

Scientists conducted the survey following a Los Angeles Times report last year that a University of California Santa Barbara professor had found evidence that barrels of DDT were dumped into the ocean.