Two teenage girls have been arrested in the US in an apparent foiled plot to kill several school students.

Officials in the state of Florida say the two girls, aged 11 and 12, were waiting in the school bathroom to attack younger students at Bartow Middle School.

The two girls were detained on Tuesday after a teacher received information that one student told another not to come to a certain area of the school as "something bad was going to happen".

This was then reported to the principal and authorities were informed.

When one of the students was noted absent from a morning class on Tuesday, a search was carried out and the girls were found in the bathroom.

The girls had a goblet or glass with them.

The pair were taken to the principal's office and were asked to empty their pockets.

A knife and sharpener were recovered from one of the girls.

Asked by Principal Roberts why she had a weapon, she replied that she and the other girl were planning to attack and kill as many students as possible.

During a follow-up search by police, officers recovered several knives - including a butcher knife.

Plans to kill 'at least 15 people'

Bartow Police Chief Joe Hall told a press conference: "Both juveniles were interviewed last night by detectives and both juveniles said that they had been planning an attack on other students over the past couple of days.

"They noted that they wanted to kill at least 15 people, and were waiting for the opportunity to find smaller kids that they could overpower to be their victims.

"Both juveniles stated that they are practicing Satanists".

Searches of the homes of the teenagers uncovered a hand-drawn map of the school that included the phrase 'go to kill bathroom'.

While mobile phone records also uncovered conversations regarding the same plot on social media.

It is believed the girls had planned to take their own lives afterwards.

They have been arrested and charged with conspiracy to commit murder and possession of a weapon on school property.