BELGRADE, Serbia (AP) — A fire in a northern Serbian city early Friday killed six people, including four children, police said.

The fire erupted around 3 a.m. in Novi Sad, some 90 kilometers (54 miles) north of Belgrade, the capital, said the Interior Minister Ivica Dacic.

An emergency doctor told state television channel RTS that all the victims were already dead when the medical team reached the scene.

Dacic said in a statement that initial findings suggest the cause could have been a charging electric scooter.

The children were between 2 and 7 years old, said Dacic.