By Alex Dobuzinskis

LOS ANGELES (Reuters) - An oil spill of 700 barrels of crude spilled from a pipeline near California's coast on Thursday but was quickly contained in a dry creek bed and did not reach the Pacific Ocean in Ventura County, officials said.

The Ventura County Fire Department had initially estimated the size of the leak from the Crimson Pipeline at 5,000 barrels, but later said a much smaller amount was released in a stain stretching a half-mile.

The line was shut shortly after the discovery of the spill, which was a tiny fraction of an infamous offshore blowout in 1969 that spewed up to 100,000 barrels into the ocean and halted new drilling in California by galvanizing environmentalists.

Thursday's leak occurred near Ventura, California, a beachside community less than 60 miles (97 km) northwest of Los Angeles.

The pipeline supplies crude to Tesoro Corp's 257,300 barrel per day (bpd) Los Angeles refinery, but was not expected to impact the refiner's ability to supply its customers, a representative for the refiner said on Thursday. Like other California refiners, it relies heavily on crude tankers arriving by sea.

Crimson took responsibility for the spill but did not say whose crude it was transporting.

Spotters stationed along the coastline, which is about a mile from the site of the leak, said no oil had reached the ocean, Doug Allen, a supervising pipeline safety engineer for the state, said in a phone interview.

Crews created an earth-filled dam about a quarter mile from the site of the leak to capture the oil, Allen said.

"It seems like they stopped it," said Allen, who is with the California Department of Forestry and Fire Protection, which has jurisdiction over the pipeline.

The oil leaked into the Prince Barranca, a gorge, and by mid-morning had been contained, the Ventura County Fire Department said.

The spill comes less than a year after a pipeline owned by Plains All American Pipeline ruptured in Santa Barbara County, just northwest of Ventura County, sending up to 2,500 barrels of crude gushing onto the shore and into the Pacific Ocean.

Plains was indicted on 46 criminal charges as a result of the spill, including four felonies for knowingly discharging a pollutant into state waters. If convicted, the company could face penalties of between $1 million and $2.8 million.

Thursday's spill is not expected to impact supplies to Southern California refineries, which each day normally process more than 1 million barrels.

Refiners in California receive large volumes of Alaskan crude and foreign oil at ports in Los Angeles, Long Beach and San Francisco Bay, in addition to volumes received by pipelines.

Public agencies, including the Department of Fish and Wildlife, the Office of Spill Prevention and Response, Ventura County Office of Emergency Services (OES), the U.S. Coast Guard, State Parks, and local government all responded to the incident, reported around 5:30 a.m. local time.

The Pipeline and Hazardous Materials Safety Administration (PHMSA) said it had sent investigators to provide assistance to the California state fire marshal, who is responsible for the investigation of the spill to determine the cause.

(Reporting by Alex Dobuzinskis in Los Angeles, Liz Hampton and Erwin Seba in Houston, and Arpan Varghese in Bengaluru; Editing by Terry Wade and Chris Reese)