Seven teenage suspects were arrested in relation to the fire at a religious school that killed 23 people, mostly students, Malaysian police said Saturday.

Police arrested the seven suspects, aged between 11 and 18, after obtaining surveillance videos from a neighboring house, Kuala Lumpur police chief Amar Singh Ishar Singh told a press conference.

The suspects are believed to have quarrels with the students at the religious school and started the fire in retribution, Amar Singh said.

Six of the suspects tested positive in drug test, he added.

A total of 21 students aged 6 to 17 and two teachers were killed in the early morning fire on Thursday near downtown Kuala Lumpur.

The fire shocked Malaysia, triggering calls to strengthen fire safety measures at religious schools across the country.