(CNN) -- At least 12 people were shot at a Tucson grocery store on Saturday, and U.S. Rep. Gabrielle Giffords was among them, a Democratic party source told CNN.
There were conflicting reports about Giffords' condition. Giffords' press secretary said the congresswoman remained in surgery Saturday afternoon for her injuries, disputing an earlier report from a law enforcement source saying she had died.
The party source described the situation as "pretty serious."
At least 11 others were shot in the incident, which happened shortly after 10 a.m. MST, Pima County Sheriff's Department spokesman Jason Ogan said.
AZ congresswoman among 12 shot in Tuscon Several shot at Tuscon grocery store
Giffords, 40, was holding a constituent meeting at the Safeway grocery store when the shooting occurred, according to a schedule posted on her website.
The Tucson Citizen newspaper reported that Giffords was shot in the head.
An FBI spokesman said the agency was sending agents to the scene, and two senior Obama administration officials said the White House is monitoring the situation. They said they believed that a congressional staffer may have been killed.
Pictures from the scene showed a Giffords banner hanging from the storefront.
At least two victims with gunshot wounds were transported at Northwest Medical Center, according to spokesman Richard Parker.
The conditions of the 11 others shot were not immediately known.
The motive for the shooting is unclear, Ogan said.
"We're just trying to sort this out right now," he said.
An employee of a nearby business, Jason Pekau, told CNN that he did not see the shooting, but heard "15 to 20 gunshots."
Giffords, a Democrat, was first elected in 2006. She has served as chairwoman of the House Space and Aeronautics Subcommittee and also holds seats on the House Science and Technology and Armed Services committees.
She won her third term in a closely contested race against a Tea Party-sponsored candidate and was one of three Democratic legislators who reported vandalism at their offices following the March vote on health care reform.
She is married to Navy Capt. Mark Kelly, a NASA astronaut who is scheduled to lead a space shuttle mission to the International Space Station.
