SEOUL - A teacher at a South Korean elementary school has admitted to stabbing a seven-year-old girl who was found in cardiac arrest and later died in hospital, a police official said on Tuesday.

The female teacher, who is being treated for self-inflicted wounds in hospital, has not yet been arrested, said the official, as police were still investigating Monday's stabbing.

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Acting President Choi Sang-mok offered deep condolences during a Cabinet meeting over the child's death and ordered the education ministry and the authorities to thoroughly investigate the incident at the school in the city of Daejeon.

The girl was a student at the school where the teacher worked, though police had not established a personal relationship between the two so far, according to the police official.

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The girl was discovered by her grandmother, an official at the Daejeon Metropolitan Office of Education said during a media briefing on Tuesday. She was found with stab wounds in the neck and face, a local fire department official told Reuters on Monday, and later died in hospital.

The female teacher had taken a leave of absence for medical reasons before prematurely returning to work late last year, the education office official told the briefing.