A 16-year-old girl poured gasoline on two Pennsylvania high school security guards and unsuccessfully tried to ignite it using a grill lighter, police said Tuesday in announcing charges against the girl.

Wilkinsburg student Imani Knight-Brantley was jailed, unable to post $100,000 bail, after being arraigned Tuesday and charged as an adult with aggravated assault, risking a catastrophe, reckless endangerment and bringing a weapon onto school property.

Knight-Brantley carried a 2-liter soda bottle filled with gasoline and the lighter in her hooded sweatshirt before attacking the guards, Brandon Murray and Leah Pyle, on Monday morning, Wilkinsburg police said in a criminal complaint.

Online court records don't list an attorney for Knight-Brantley, who was interviewed by police while accompanied by her grandmother, the girl's legal guardian, according to the complaint.

Although Knight-Brantley acknowledged pouring the gasoline on Murray — with some spilling on Pyle — she told police she had been provoked during a confrontation with Murray on Friday.

Murray told police he escorted Knight-Brantley from school on Friday for using her cellphone, a rules violation. The school — one of the poorest in the Pittsburgh suburbs — has an after-school food program and the suspect returned at the end of the day to eat before milling about when other students began fighting that afternoon, Murray told police.

Murray told police the girl became upset when he again escorted her from school property, told her she was being suspended and had to return Monday with her guardian. The girl screamed at him and threw an open milk carton, which hit him in the head, Murray told police.

Knight-Brantley told police she threw the milk at Murray only after he slapped a food tray she was holding, and that he also put her in a headlock and threatened to bite her. She also told police that a friend overheard Murray using a crude term to describe her.

The girl said "this angered her and she could not wait to see Murray on Monday," the criminal complaint said.

The girl's grandmother told police that neither her granddaughter nor the school told her about the Friday confrontation.

OSA Global, the New Castle company that contracts to provide the school guards, did not immediately return a call for comment.

School spokesman Pete Camarda, who told reporters Monday that the girl hadn't attempted to light the gasoline, said Tuesday, "As the day unfolded, we found out more and more."

Murray was working Tuesday but was unlikely to return to the school on Wednesday, Camarda said.

"As we're looking into this, he may not be here tomorrow," Camarda said. "You have to take action while you're assessing what went on."

The girl wouldn't tell police where she got the gasoline, but she acknowledged confronting Murray on Monday, then throwing gasoline onto him, hitting the other guard and soaking the floor. Officials evacuated the school and classes were canceled for the day as the smell of gas permeated the building.

Murray said Knight-Brantley tried to activate the lighter, but Pyle knocked it out of the girl's hand.

Asked by police whether she "intended on igniting" Murray, the girl said, "yes."