A sixth-grade girl pulled a handgun from a backpack at her eastern Idaho school on Thursday and opened fire, hitting two fellow students and a member of school staff and inflicting non-life-threatening injuries on them, officials said.

The girl was disarmed by a teacher at Rigby Middle School in Rigby, Idaho, a remote community about 270 miles (435 km) east of Boise, and held until law enforcement arrived, Jefferson County Sheriff Steve Anderson said. Her name and exact age weren't immediately released.

"She fired multiple rounds inside of the school and out," Anderson said at a news conference. "We don't have a lot of details of why. That is being investigated."

Students were sent home with their parents immediately after the shootings and classes will be canceled on Friday, Jefferson School District Superintendent Chad Martin said.

"This is the worst nightmare any school district could ever face," said Martin. "We prepare for it and we're never truly ready for it."

Several law enforcement agencies are involved in the investigation of the shooting, which happened shortly after 9 a.m. local time, Jefferson County Sheriff Anderson said. Local media had previously reported that a male student was taken into custody after the shooting.

Depending on the outcome of the investigation, Jefferson County Prosecuting Attorney Mark Taylor said charges against the girl could include three counts of attempted murder.

None of the gunshot wounds were life-threatening, Michael Lemon, trauma director at Eastern Idaho Regional Medical Center said.

"They could be so much worse," Lemon said. "We feel absolutely blessed."

The school staff member was treated and released for his injury, while the two students were being kept overnight for observation, he said.

Idaho Governor Brad Little issued a brief statement shortly after the incident.

"Thank you to our law enforcement agencies and school leaders for their efforts in responding to the incident," Little said on Twitter. "I am staying updated on the situation."