Around 9:30 p.m., Shoreline security called police for aid because three people had been stabbed inside the theater on the lawn area at 1400 North Shoreline Boulevard.

"There were fights breaking out. I'm not exactly sure why," said Wes Fifield, director of Rock Medicine, a group that provides medical assistance at concert events. "There was, of course, one on the grass, and one up on the fenceline, and even one on the concourse."

The stabbings were separate, but two might have been among people in the same group, police spokeswoman Liz Wylie said.

The victims were all taken to a hospital and are expected to survive.

The theater has its own law enforcement agents inside, but police had been helping them contain fights that had been breaking out throughout the night.

Mountain View police first started helping tame the fights around 6:30 p.m., and had left by the time the stabbings were reported because they thought the fights were under control, according to Wylie.

After the stabbings, six other agencies responded to help with security in case a riot broke out, including the Santa Clara County sheriff's department, the CHP, and the Palo Alto police department.

Concert organizers let the band finish playing but turned on the lights and announced they would close the theater promptly at 10:15 p.m.

No suspect information was available.

Police say they expect a lengthy investigation, as those they believe were involved were not cooperating.