An overnight fire a primary school dormitory in Uganda killed 19 school children and two adults, police said Tuesday.

By the time the fire brigade reached the school, most of the girl's dormitory had already burned down at the school about 7 1/2 miles from the capital, Kampala. The students were between the ages of 7 and 10 and the adults were their matrons.

Police spokeswoman Judith Nabakooba said authorities were investigating the cause of the blaze.

The doors to the dormitory had been locked from the outside and there was no electricity during the time of the fire, said school worker James Kiiza.

"We suspect that bad people are responsible for the fire," he said. "We cannot say it was due to electricity short circuit. And the door was locked from outside, which shows that someone could have first locked the door before setting the fire."

Kiiza said there were few people around because workers have been on strike for more than a month because they have not been paid, a common occurrence in Uganda.