A Chester County teacher is facing criminal charges after she was found passed out, drunk, in a high school chemistry lab, Tredyffrin Township police said.

Carol Wittschieben, 42, was charged with endangering the welfare of children, disorderly conduct, and public drunkenness after the incident Dec. 10 at Conestoga High School, where she is a chemistry teacher.

According to an affidavit of probable cause, Wittschieben was teaching a sixth-period Advanced Placement chemistry class around noon when a teacher stopped by her room to check on her after another teacher noticed that she seemed ill.

The 11th- and 12th-grade students were taking a test in the chemistry lab, but Wittschieben was not in the room. The teacher entered the room, found Wittschieben unresponsive on the floor of an adjoining lab prep room, and called 911. Students do not have access to the prep room, the affidavit stated.

According to the affidavit, Wittschieben was taken to Paoli Hospital in an ambulance and told a medic en route that she was an alcoholic and had been drinking throughout the day. She told the medic she had been drinking from a water bottle in her purse; police later confiscated the bottle, which was filled with what smelled like an alcoholic beverage, according to the affidavit.

According to the affidavit, a toxicology report showed that Wittschieben's blood-alcohol content was 0.32 percent.

She was later charged via summons and is expected in court Jan. 23. Conestoga officials said they were cooperating fully with police and had placed Wittschieben on leave.

Wittschieben declined comment when reached at her Wayne home Thursday. Conestoga officials would not comment on her replacement.

"The district takes matters of student safety very seriously, and we have and will continue to cooperate with the police investigation," they said in a statement posted on the school's website.

Conestoga has an enrollment of about 2,000 students and has been ranked the No. 3 high school in the state by U.S. News and World Report.

Contact Aubrey Whelan at 610-313-8112, at awhelan@philly.com or on Twitter at @aubreyjwhelan.