A pack of up to four pit bull terriers has been blamed for the death of a jogger in rural Los Angeles, with officials warning on Thursday that the dogs remained on the loose.

Sheriff's Lieutenant John Corina said a woman in a car saw the dogs attacking the female jogger, 63, on Thursday morning. The witness called police and blew her car horn to try to get the dogs to stop.

"When the first deputy on scene saw one dog still attacking the woman, he tried to chase the dog away," Corina said. "The dog ran off into the desert, then turned around and attacked the deputy, the deputy fired a round at the dog and tried to kill the dog, and the dog took off into the desert."

The woman died while she was in an ambulance on the way to a hospital, said Evelina Villa, county animal control spokeswoman.

The coroner's office was investigating to determine the cause of death.

Sheriff's officials were alerting people in the area to watch for four tan-coloured dogs and were using a helicopter to search for them. It was unclear whether the dogs had collars or owners.

"In these areas you might have a situation where people dump animals out in rural areas," said John Mlynar, a spokesman for the nearby city of Palmdale. He had never heard of an attack like Thursday's, Mlynar said.

Residents near the site of the attack said stray dogs were constantly roaming the area and had attacked people before. "It's really scary," Diane Huffman, of Littlerock, told KABC-TV. "I don't know what to think. I really think I'm going to be getting a gun to protect myself."