Jakarta. At least eight young students died after a fire broke out at an Islamic boarding school in Karawang, West Java, on Monday.

Police said the victims are aged between seven and 13 years old and they were having a nap when the second floor of Miftahul Khoirot Islamic School building caught fire.

The flames began at around 1:00 p.m. reportedly because of a faulty electric fan that ignited a fire and burned a mattress before developing into a disaster, Karawang Police Chief Adjunct Chief Commissioner Aldi Subartono told Kompas news website.

He said two other students were hospitalized with minor injuries, adding that an investigation is underway to determine the cause of the deadly blaze.

The district fire department received a call around 30 minutes after the fire started to engulf the upper part of the building. It took about an hour for firefighters to put out the fire.

The school has four separate buildings and the one engulfed in flames was occupied by younger students.

“The incident occurred at around the midday break so the majority of students were having a nap,” a student identified as Yanyan Bahari, 15, told Kompas.

Islamic boarding schools typically start very early when Muslims have their dawn prayer and it’s very common that their students use midday break to have a short sleep.