Portugal Colonial - 'Gigantic explosion', fire in Dutch city, four hurt

"After the explosion, several buildings collapsed. Four people were injured. They were taken to the emergency hospital," the local emergency services department said in a statement.

It was not immediately clear what caused the blast nor whether there were more victims.

Officials called on the local population to stay away from the area, as emergency services rushed to the scene.

"The fire department is currently investigating how the collapsed and damaged buildings can be safely searched to determine if anyone is still inside," authorities said.

"Extensive damage is reported in the surrounding area."

An AFP reporter on the scene saw several firefighters with ladders trying to access buildings.

Shattered glass littered the streets that were cordoned off to the public, according to this reporter.

"It's also possible that there are still people under the rubble," city mayor Sharon Dijksma told public broadcaster NOS.

TV images showed a plume of smoke rising above the historical city centre and rubble strewn across the streets.

"I knew right away that this was bad," NOS quoted one witness, Margot Schroevers, as saying.

"The ground was shaking," she said.

The local hospital in Utrecht has set up an emergency trauma centre. The Red Cross urged volunteers to head there as soon as possible.

M.A.Vaz--PC