SAN FRANCISCO -- A baby bison in Golden Gate Park died Wednesday night after being found with three broken ribs following an incident in which a small dog got into the bison paddock, officials said today.

Park patrol officers found the dog, identified as a toy breed, running inside the back of the paddock at about 9 a.m. Wednesday, said officials with the Recreation and Park Department. The dog's handler was trying to coax out the dog, which appeared to have burrowed under the paddock fence, officials said.

Zookeepers from the San Francisco Zoo examined the herd for injuries and found a laceration on the left side of a 6-month-old female bison. The bison had three broken ribs, and after it was treated, it rejoined the herd.

The baby bison was found dead a few hours later, at about 5:20 p.m.

It was not immediately clear whether the dog was responsible for the bison's injuries. A necropsy was scheduled for later today.

Park patrol officers said the dog handler had five dogs off their leashes. The handler was cited for animal disturbance and failure to use a leash in a designated on-leash area.

The baby bison was one of seven brought in from a Redding ranch in November, in an effort to rejuvenate the dwindling Golden Gate Park herd, said Connie Chan, Recreation and Park Department spokeswoman. Six of the bison were bought for $1,200 each with the fundraising help of Assemblywoman Fiona Ma. D-San Francisco, and the seventh was donated.

Ma said in a statement today that she was "disheartened by the unfortunate accident. ... This is a sad reminder that we must be responsible pet owners at all times - especially when going out to parks where there are children, pets and other animals."

The young bison are kept in a separate area from the adults in the paddock. A fenced-in, off-leash dog play area is about 50 feet north of the young bison paddock.

Katie Kindt, a 49-year-old dentist who lives in San Francisco, walks her wirehaired vizsla and vizsla twice a day in the park. Today, she had them off leash just outside the paddock fence.

Kindt said she always follows signs for on-leash areas that are clearly marked. "There's one guy who ruins it for everyone else," she said of those who can't control their dogs while off-leash.

Kindt said professional dog walkers should be licensed. A proposal requiring licensing and training for commercial handlers - and capping the number of dogs at a time at eight - is up for approval before the Board of Supervisors this month.