Wellington, Jan 27 NZPA - Environmental samples taken after a fire at the former Waipukurau Hospital on Monday have confirmed that no contamination of asbestos occurred off site.

Hawke's Bay District Health Board medical officer of health Nicholas Jones said sample results returned today showed no asbestos was present in the ash.

Dr Jones said samples were taken as a precaution and collected at multiple sites ranging from very close to about a kilometre away from the site of the fire.

Air sampling would be carried out over the next few days to ensure the fire had not disturbed any other asbestos, but the risk of this was very low, he said.

The DHB's public health unit was now working with the property owner as well as Central Hawke's Bay District Council, the fire service and other government agencies to reduce the risk the property now posed to public health.

"Buildings on the site are generally in a state of disrepair and very dangerous," Dr Jones said.

"Many are known to contain asbestos. The public should stay away from the site and prevent exposing themselves to asbestos and falling debris."

Central Hawke's Bay District Council's chief executive John Freeman also urged the public to stay away.

"Please take these warnings very seriously. Signs have been erected warning the public of the danger and people should keep out. Anyone who doesn't adhere to those notices would be on the property at their own risk," he said.

Property owner Jason Dempsey also asked the public to remember the site was private property and anyone entering the former Waipukurau Hospital without permission could be charged with trespass.

Meanwhile, police say the occupants of a car parked near the suspicious fire on Monday may have information vital to arson inquiries.

Firefighters discovered the main three-storey building and a smaller nearby building alight when they arrived about 1.30am on Monday, sparking suspicions the fire may have been deliberately lit.

A firefighter from the first crew to reach the blaze saw what was believed to be a white Mitsubishi station wagon parked inside the hospital grounds with two people in it, Detective Glen Yule of Hastings police said.

Police would like to speak with the occupants.

"We just need to eliminate them from our inquiry, to find out what they've seen. They might have just been passing by, I don't know, but we would like to speak with them," Mr Yule said.

Police were "keeping an open mind" about whether the suspicious fire was linked to the robbery of a Post Shop on the main street of Waipukurau, also on Monday morning, Mr Yule said.

The man entered the shop at 9.27am and demanded money from staff before walking back out and disappearing.

He had oil or soot on his face and was wearing a black hooded sweatshirt with yellow and white flames down the side and carrying a black and silver backpack.

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