Marine rescuers have again lost a blue whale last seen dragging fishing line off Mexico's Pacific coast — and the buoy they fastened to the line can't track its movements.

Rescuers couldn't free the 80-foot whale first spotted Friday off Los Angeles. With darkness falling, they attached a bright red buoy, hoping that would help them find it again.

But there has only been one sighting since — on Monday, off northern Baja California, more than 100 miles south of Los Angeles.

Jim Milbury of the U.S. National Oceanic and Atmospheric Administration said the U.S. rescue team didn't attach a tracking buoy because those weigh about 50 pounds, adding to the whale's burden.

Rescuers in Mexico say they are too far from the last sighting to head out.