At least four people have been injured in an explosion and fire in central Utrecht on Thursday afternoon, regional safety board officials told broadcaster NOS.

The blast, in a building on the Visscherssteeg, sent glass and debris showering onto the street. “The ground shook,” eyewitness Margot Schroevers told NOS.

Utrecht mayor Sharon Dijksma told reporters it is still too early to say how much damage has been caused and how many people have been injured. An investigation is under way and some people reported smelling gas, she is quoted as saying.

Sources in The Hague told RTL there is nothing to indicate the blast was deliberate or linked to terrorism.

Eyewitnesses spoke of chaotic scenes, describing broken windows and chunks of masonry on the street.  Waitress Anna in nearby cafe Little Dublin told RTL she heard a loud boom. “The doors opened and the windows shook,” she said.

Initial reports suggested there had been two explosions, but that is now in doubt, NOS said.

By 5.30pm, the fire brigade was able to enter the building where the blast had taken place. It is not yet clear if anyone is under the rubble.