Nurses and building operators at two Sonoma County hospitals have walked off the job in a three-day strike to protest wages and other issues.

Officials with the Staff Nurses' Association and with the Stationary Engineers say the nurses and workers at Santa Rosa Memorial and Petaluma Valley started the strike at 5 a.m. Saturday.

The Santa Rosa Press Democrat says both unions called for the walkout because of demands by hospital officials for cuts in on-call and night shift pay, as well as proposed reductions.

But hospital officials say the hospitals are operating with narrow profit margins, and they need to invest in new technology.

The Staff Nurses' Association represents about 660 nurses, while the Stationary Engineers Local 39 represents 17 engineers at Memorial and three at Petaluma Valley

Hospital officials say they have arranged for replacement workers.