SEACLIFF, Calif. (AP) _ Railroad officials acknowledged they have no idea when the wreckage of a derailed freight train will be cleared enough to allow a coastal highway to reopen.

''Given our track record, we'd rather not give an estimate,'' said Robert Hoppe, spokesman for Southern Pacific Transportation Co., as emergency work dragged into an unexpected fourth day Wednesday.

A 10-mile stretch of U.S. 101 has been closed since 14 cars of a 42-car Los Angeles-to-Oakland train jumped the tracks at midday Sunday, piling up beneath a freeway overpass 60 miles northwest of Los Angeles.

Four of the derailed cars carried hazardous materials, including hydrazine, a jet fuel additive that is a suspected carcinogen and can be deadly.

Michael Lindbery, spokesman for the Ventura County fire department, said it took various agencies a long time to agree on a plan to remove chemicals and clean up the ground where 440 gallons of hydrazine spilled from ruptured drums.

Fire dispatcher Paula Aliano said Wednesday night that the drums were being placed into larger barrels that can then be hoisted out of the wreckage, but she didn't know when the process would be complete.

The California Department of Transportation will then examine a freeway overpass support to assess its integrity. The next step will be removal of the derailed cars, then examination of the track for damage.

Hoppe said the rail line, a major north-south artery carrying both freight and passengers, could be reopened rather quickly.

The derailment apparently occurred when a bearing overheated and snapped an axle off a car, said Claire Austin, spokeswoman for the Federal Railroad Administration.

It was the second Southern Pacific freight train derailment in California this month. On July 14, a tank car derailed in the Sacramento River Canyon, spilling a pesticide that killed wildlife along a 45-mile stretch of the river.