An oil slick is seen along the coast of Refugio State Beach in Goleta, California, United States, May 19, 2015. A pipeline ruptured along the scenic California coastline on Tuesday, spilling some 21,000 gallons (79,000 liters) of oil into the ocean and on beaches before it could be secured, a US Coast Guard spokeswoman said. [Photo/Agencies]

GOLETA, California - A broken pipeline spilled 21,000 gallons (79,500 liters) of crude oil into the ocean before it was shut off Tuesday, creating a slick stretching about 4 miles (6.4 kilometers) along the central California coastline, the US Coast Guard said.

Authorities responding to reports of a foul smell near Refugio State Beach around noon found a half-mile (800-meter) slick already formed in the ocean, Santa Barbara County Fire Capt. Dave Zaniboni said. They traced the oil to the onshore pipeline that spilled into a culvert running under the US 101 freeway and into a storm drain that empties into the ocean.

The pipeline was shut off about three hours later but by then the slick stretched four miles (6.4 kilometers) and 50 yards (45 meters) into the water.

The 24-inch (60-centimeter) pipeline is owned by Plains All American Pipeline, which said it shut down the flow of oil and the culvert carrying the oil to the ocean was blocked.

"Plains deeply regrets this release has occurred and is making every effort to limit its environmental impact,'' the company said in a statement.