TEMPE, Ariz. -- Tempe firefighters said a mercury spill forced them to evacuate and shut down the city’s library Thursday afternoon.

Firefighters said library staff called emergency crews are mercury was found on a keyboard around 1 p.m.

When firefighters arrived, they found more mercury in the building’s entrance and parking lot.

About 200 patrons and staff were evacuated.

Firefighters said the spill was caused by kids playing with mercury in the parking lot Wednesday night.

Police received a 911 call around 10 p.m. reporting spilled mercury at the library.

When officers arrived, they found only a small amount of the chemical at the front of the building.

Police are now looking for the people who spilled the chemical. They say it is possible the kids could face criminal charges.

“If they did this on purpose, absolutely,” Tempe fire investigator Mike Reichling said. “We are doing a full investigation between the fire department and the police department here in Tempe to get to the root of this. If this was a malicious act, it would be criminal.”

Reichling said the amount of mercury spilled has not created a serious health hazard.

“These amounts are very minute. If someone did have contact here, wash their hands and wash their clothes. They should be fine,” he said.

The city has hired a crew to clean up the mercury spill.

The Tempe library is expected to reopen at 9 a.m. Friday.