A headmaster from a Chelyabinsk school caused a storm Wednesday when it became known that he refused a police request to draw up a list of his students' ethnicity — arguing that the only ethnicity at his school was math.

Alexander Popov confirmed Wednesday that he had sent a reply to the local police precinct in the Urals city saying that "there is only one ethnicity in our school — mathematics," Interfax reported.

Popov's school, the Chelyabinsk Lyceum No. 31, is a high school specializing in mathematics and physics.

He said he had received a written request from local police in which he was asked to list the names, dates of birth and parents' addresses of "students of Caucasian nationality" who have either Russian or foreign citizenship.

Scans of the police letter, dated May 16, and the headmaster's May 21 reply were published online by regional media.

Popov said Wednesday that he had no idea why the police needed the information, but that this was not the first time he had received such a request.

"In 2008 when the conflict over South Ossetia heated up, I was asked to give information about Georgians," he told the Ura.ru news website. He added that at the time he replied that there were Cumans — a nomadic people that roamed the region in the Middle Ages — at the school.

Chelyabinsk police would not say Thursday why the letter was sent but admitted that it was improper.

"There is an ongoing internal investigation as to why the request was issued in such an incorrect form and what its aim was," police spokeswoman Anzhelika Meshcheryakova told Interfax.

She added that it was normal for police to give extra attention to students before the three-month summer vacation, which starts at the end of this week.

"Children will spend more time on the streets. During this time we always do more to prevent crimes both committed by them and against them," Meshcheryakova said.

However, an unidentified police spokesperson told Ura.ru that the request was aimed at uncovering illegal migrants.

"The letter was about citizens of republics like Azerbaijan, Georgia and Central Asia who need to register here," the spokesperson said. "We admit that the letter was not formulated correctly and competently. This is because its author was not experienced."