OAKLAND, Calif.—A complaint has been filed on behalf of thousands of University of California hospital workers who claim they were threatened when they went on a two-day strike in May.

The American Federation of State, County and Municipal Employees, which represents some 13,000 hospital pharmacists, nursing assistants, operating room scrubs and other health care workers, took the claims to the state Public Employment Relations Board.

Last week, the board issued a complaint to force UC to answer the allegations.

The complaint outlined alleged instances when UC administrators questioned workers about their participation in the walkout, told them their absence during the strike would be considered unauthorized, and threatened disciplinary action.

UC spokeswoman Dianne Klein said Tuesday the administrators believe they acted in accordance with the law.

"We have negotiated tirelessly and we are going to respond appropriately to this," Klein said about the complaint.

The union organized the strike at medical facilities in San Diego, Orange, Los Angeles, Santa Monica, San Francisco and Sacramento.

The union was battling the university system over staffing and pension issues.

Nurses did not strike and emergency rooms were open, but the walkout prompted the postponement of non-essential surgeries.

A settlement conference will be held to resolve the allegations made in the complaint, Klein said. If the case can't be resolved, an evidentiary hearing will be held before an administrative law judge.