THE HAGUE -- At least four people were injured in an explosion and major fire in the Dutch city of Utrecht on Thursday afternoon, local authorities said.

A spokesperson for the Utrecht safety region said at least four people were injured in the explosion till 17:30 local time (1630 GMT). The severity of the injuries is unclear.

According to Dutch public broadcaster NOS, the municipality and the safety region of Utrecht reported that a very large fire was raging in a house after "people heard a loud bang."

Firefighters are still working to extinguish the fire. At least 10 ambulances are on the scene. Several streets around the building are closed. The University Medical Center in Utrecht is opening a special department in the hospital following the explosion and fire.

"Exactly how many buildings and which ones are damaged is not entirely clear at this time." Utrecht Mayor Sharon Dijksma told local media.

The cause of the explosion remains unclear.