ABC News' Dina Abou Salem reports:
At least two robbers wearing black hoods hit the California Mining and Minerals Museum in broad daylight, using pick axes to break open the displays, officials said.
California investigators are still searching for the suspects who robbed what police estimated to be $2 million in gems from the museum, operated by the California Department of Parks and Recreation.
"We do not have a listing of items or the [value] of the amount stolen yet, as we are beginning a detailed inventory this week," the department's deputy director of communications, Roy Stearns, told ABC News.
"The two people who work for state parks that were in the museum at the time of the robbery are shaken, but are not injured," Stearns added. "The museum is now closed and will remain closed until further notice for repairs."
The California Highway Patrol's Central Division said in a prepared statement that "the suspects made verbal threats to employees at the museum during the robbery and stole an undetermined quantity of precious material."
The suspects might find difficulties selling the stolen items because it is "uncommon for most citizens to possess such minerals," authorities said. California Highway Patrol officials urged anyone approached with suspicious items to contact them.
According to the museum's official website, the robbers failed to make off with perhaps the biggest potential prize, the Fricot Nugget, a rare, 13- to 14-pound crystalline gold specimen.
Jeff from Lou's Speedie Lube and Auto Repair, a nearby business, was surprised that a robbery of such scale could happen in Mariposa County.
"We are a small town and when crimes like this happen, we all hear about it," he said. "Crime is very low here in Mariposa and I am surprised the police haven't caught them yet. I am even surprised that the thieves could even breach all the security at the museum."
The California Highway Patrol Central Division Investigative Service Unit, which was handling the investigation, was urging anyone with information to call (209) 356-2900.