The fire that destroyed a school dormitory in Uganda, killing at least 19 children and two adults, may have been started deliberately, according to police.

"Preliminary investigations indicate that it was homicide," Kale Kaihura, the police inspector general, told reporters at the school outside the capital Kampala on Tuesday.

He said that interviews with teachers and survivors led him to believe the fire was started deliberately.

Frederick Bugembe, a teacher at the Budo school, said there were 58 girls in the dormitory, but some managed to wriggle through narrow windows.

It is understood that the doors to the dormitory were locked from the outside.

The children, aged between 7 and 10 had been sleeping at the time.

Hundreds of parents arrived at the school, which has around 1,000 students, to search for their children.

"Help me, oh God please help me," Jacqueline Bakoba cried as she lifted up part of the collapsed roof looking for her missing daughter.

It was the third deadly fire at a school in Uganda in two years.