Cleanup crews scrambled to contain a nine-square-mile spill on a rural stretch of the California coastline on Wednesday, following a pipeline break that dumped up to 105,000 gallons of crude on land and into the ocean, blackening a popular state beach.

Darren Palmer, the chairman and CEO of Plains All-American Pipeline, a Houston-based company, told reporters Wednesday evening that an estimated 21,000 gallons of crude may have reached the water. The cause of the leak has not been identified, Palmer said, but shortly before the accident, he said, the company had "mechanical issues" with its pumping units.

Until then, Palmer said, the pipeline had not malfunctioned since 1987, when it was built to carry processed crude from processing plants on the coast to refineries in Texas.

"We deeply regret that this incident has occurred at all," Palmer said. "We apologize for the damage it has done to the environment. We apologize to the residents and visitors for the inconvenience it has caused, especially on this Memorial Day weekend."