(CBS) – A teacher at Lake Central High School in St. John, Ind. faces drug-related charges after allegedly being caught by students using drugs in her classroom.

The student witnesses contacted school administrators, who called St. John police, who, in turn, requested assistance from Dyer police for their drug-sniffing dog.

Arrested was 24-year-old Samantha Cox, who was led from the school at about 1 p.m. Wednesday. She faces felony drug possession and misdemeanor paraphernalia charges and is being held in the Lake County Jail.

Student John Rogers says he recorded cell video of Cox, his English teacher, snorting what police say may have been a mixture of cocaine and heroin.

“She tried to hide herself,” Rogers tells CBS 2’s Charlie De Mar. “She wasn’t at her desk where we could see her. She was all the way in the corner where she thought we can’t see her.”

Another student, Michael Sanchez, says: “It is like a serious thing. A lot of people can get addicted to a lot of things, and something like this is, it’s very heart-breaking.”

In a statement, St. John Chief James Kveton said the students showed “a tremendous amount of fortitude and integrity” by going directly to the principal.

In a robocall to parents, Lake Central Superintendent Larry Veracco said police and school staff took “swift and forceful action.”

He said safety “remains the top priority of our school staff.”

Video posted to social media allegedly shows a woman using cocaine in a corner of an empty classroom. It could not immediately be authenticated.