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Four people were injured and taken to a hospital Friday after being attacked in an RV by a pit bull who had just given birth to a litter of puppies, Riverside County officials said.

Multiple agencies responded to an emergency call in the Santa Ana River near Wilderness Avenue around 8:30 a.m., according to a news release from the Riverside County Department of Animal Services.

When they arrived, first responders found four victims — three men and a woman — with bite wounds. All four were transported by ambulance for treatment of non-life-threatening injuries, according to the release.

Authorities say the 3-year-old dog first attacked her owner inside the recreational vehicle, then bit two of the owner’s friends. The fourth victim tried to pull one of the other victims out of the RV and was bit on his arms.

Graphic photos released by Animal Services revealed a bloody scene, with red stains smeared all over the vehicle’s floor and on a grate outside.

Investigators still don’t know what prompted the first attack, but they noted that the fact that the dog had just given birth may have been a factor.

She was taken to the Western Riverside County/City Animal Shelter in Jurupa Valley and surrendered by the owner for euthanasia, according to the release.

The pit bull’s nine newborn puppies were also euthanized, Animal Services spokesman John Welsh told The Press-Enterprise.

“We would have needed a foster parent right away to bottle feed the puppies or a mother dog that would have just given birth,” Welsh explained to the newspaper.

The incident comes less than two weeks after another dog attack in the area, according to the release.

A man was fishing on the evening of July 26 when he was injured by two dogs at a location about 2 miles away from Friday’s scene.

Those dogs have not yet been found yet. However, authorities showed a photo of the female pit bull to the fisherman and he said she didn’t match either of the dogs from last week’s attack.

Animal Services used the two incidents to underscore the potential dangers of visiting the Santa Ana River bottom and urged people going there to exercise caution, especially as the two dogs in the July 26 incident are still believed to be on the loose.

“We know the Santa Ana River area is used by families recreating in the water with picnics and beach chairs,” Animal Services Lt. James Huffman said, according to the news release. “But parents should be vigilant in keeping an eye on toddlers and themselves if they come across an unleashed dog. The dog could be feral or vicious.”