Russian authorities say a teacher and two teenage boys have been seriously injured in what investigators say was a knife fight at a high school in the city of Perm.
The regional Security Ministry said that a total of 15 people, most of them students, were hurt in the incident at School No. 127 on January 15.
Initial reports cited officials as saying two masked men attacked the school in the city, which is 1,150 kilometers northeast of Moscow.
But the regional Investigative Committee branch later said that it was a fight between two students with knives and that teachers and other students tried to break it up.
Police, meanwhile, said that one of the boys involved in the fight was a former student at the school.
In a statement, the regional police said that an unspecified number of suspects were detained and that one had previously been on a register of people diagnosed as having mental-health problems.
The Security Ministry said that a female teacher and two boys, aged 15-16, suffered severe injuries.
Classes were canceled and the school was evacuated.
The Investigative Committee has opened an investigation on suspicion of attempted murder.
There were conflicting reports about whether anyone was in custody.