(CNN) Two girls at a middle school in central Florida were waiting in a bathroom, planning to overpower at least 15 smaller students, kill them with knives and drink their blood, authorities said Wednesday.

The Bartow Middle School students were arrested Tuesday and charged with conspiracy to commit murder, possession of a weapon on school property, carrying a concealed weapon, and disruption of a school function, Bartow Police Chief Joe Hall said during a news conference.

According to officials, the 11- and 12-year-old girls said they were Satan worshipers and were going to drink the blood and eat the flesh of the students they killed. The girls then planned to kill themselves, they said.

The plan was foiled Tuesday after an automated call from the school notified one of the girls' parents that the daughter was missing from class, Hall said.

The district attorney has not indicated whether the girls will be tried as adults. CNN does not name minor suspects unless they are tried as adults. It's not clear if either of the girls has retained counsel, as neither has a court date set.

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