An  underground oil pipeline that ruptured in Santa Barbara County could have released as much as 105,000 gallons of crude, with tens of thousands estimated to have gone into the ocean, officials with the the oil company said Wednesday.

The company, Plains All American Pipeline, said its scenario was based on the line’s elevation and flow rate — which averages about 50,400 gallons an hour.

Investigators won’t find a cause for the rupture until they excavate the 24-inch wide line, which was installed in 1987, according to a joint statement from government and company officials.

When the line ruptured Tuesday afternoon, the oil seeped through the ground to a culvert and flowed into the ocean outside Refugio State Beach. The company estimates about 21,000 gallons of crude went into the water.

The U.S. Coast Guard said a pair of oil slicks are stretching across a combined nine miles of coastline.