A social worker was stabbed and severely injured Thursday inside Zuckerberg San Francisco General Hospital, authorities said.

The San Francisco Sheriff's Office said at about 1:30 p.m., hospital workers requested additional security for a doctor who had received threats from a patient. While providing security for the doctor, a deputy heard a disturbance in a hospital hallway involving a suspect and the social worker from the University of California, San Francisco, the Sheriff's Office said.

The deputy immediately intervened and restrained the suspect, while medical staff on site tended to the 31-year-old social worker, who was stabbed in the neck and shoulder, the office said. The unidentified social worker was listed in critical condition.

Deputies recovered a five-inch kitchen knife believed to have been used in the attack. The 35-year-old male suspect was at the hospital for a scheduled appointment and had reportedly made previous threats to the doctor, the Sheriff's Office said.

There was no ongoing threat to the public, the office said.