The Hague (AFP) - Dutch authorities said on Sunday they believed an explosion and inferno that caused an apartment block to collapse killing at least five people was a criminal act.

Rescue workers were combing through the wreckage in a bid to recover bodies from the blast that levelled five homes early Saturday, but the number of people possibly still buried in the debris was unknown.

“What caused the explosion is still unknown. What is clear to us is that there are indications that it is a crime,” chief public prosecutor officer Margreet Froberg told reporters.

“What these indications are, we cannot yet share in the interest of the investigation. As soon as we can, we will of course do so,” she added.

Five bodies have so far been pulled out of the husk of the three-storey apartment block. One person was hauled out still alive and rushed to hospital.

There are a total of four injured people in hospital but authorities said the intensity of the blaze made identifying victims only possible via DNA records.

This in turn complicated calculations as to how many people could still be missing in the disaster.

Hague police chief Karin Krukkert said investigations were focused on a car seen speeding away from the scene shortly after the explosion at 6:15am (0515 GMT) on Saturday.

“Clearly, we would very much like to speak to the driver” of this vehicle, she said, although the link between the car and the building explosion remained unclear.

Two separate teams have been established, one to identify victims and another to investigate what caused the explosion, she said, warning the probe would last a long time.

- ‘Total chaos and destruction’ -

City mayor Jan van Zanen said the elite recovery teams working on site were scouring the basements of the collapsed building in a final bid to locate bodies.

He said that work should be completed overnight or early in the morning.

“We are witnessing an unprecedented disaster here… the suffering is incalculable,” said the mayor.

He praised the solidarity of his city’s citizens, including a crowdfunding effort that has garnered more than 300,000 euros ($317,000) from more than 10,000 people.

The three-storey building consisted of shops on the ground floors and five two-storey apartments, authorities said, with living rooms on the second floor and bedrooms on the top.

Residents told local media the apartment block was mainly inhabited by elderly people and families with children.

Around 40 residents of other blocks near the collapsed building have been evacuated. Some have been taken away by bus to an unknown location.

Froberg, chief public prosecutor officer, described the events that rocked the city before daybreak on Saturday as “unimaginable and terrible.”

“One moment you are lying quietly in your warm bed and the next moment total chaos and destruction,” she said.