The findings, subsequently backed up by similar tests in Norway, Britain and two other countries, triggered a worldwide food scare.

"Acrylamide is of high concern because it can cause cancer in animals and probably causes it in human beings," Jorgen Schlundt, the U.N. body's food safety programme coordinator, told a news conference.

But he said it was early to draw firm conclusions and make recommendations to the public about their eating habits.

Scientists are unclear exactly how acrylamide is formed. It seems to be produced when starchy foods like potatoes, rice and cereals are fried or baked.

The U.S. Environmental protection Agency classifies the substance, used in some colouring and glues and for water purification, as a "medium-hazard probable human carcinogen".

After three days of closed-door talks, experts said they needed to know more about how it was formed, and at what temperatures, as well as the types of foods involved - research which could take from weeks to a couple of years.

"On the information we have at the moment, we cannot give consumers very specific advice such as to avoid eating chips of this or that brand," said Dieter Arnold of Germany's Federal Institute for Health Protection of Consumers, who chaired the experts' meeting.

HIGH CONCENTRATION

Stockholm University researchers found that an ordinary bag of potato crisps may contain up to 500 times more acrylamide than the maximum concentration the WHO allows in drinking water.

But the experts said tests on food were more complex than those for water and there were still many gaps in scientists' knowledge, including what the real danger level was.

"You should not have a picture that if you eat something once that has acrylamide then you will get cancer tomorrow. It is clear that the longer you eat it, the greater the risk," Schlundt said.

He said that experts were calling for an international network of laboratories to be set up to pool information, including data from national authorities and industry.

Industry should also carry out its own investigations into food processing methods, the experts said, adding that it was already known that lots of foods could cause cancers.

"We need to do research quite urgently in order to be able to reduce the levels (of acrylamide) in food," Arnold said.

"We know we get a lot of cancers from food, some of it might come, or it is very likely that it does come, from acrylamide. If we can modify the ways we produce food, so that we get less acrylamide, we will have less cases of cancer," Schlundt added.

But the toxicology studies could take months or even years to complete, the two officials warned.

In the meantime, consumers should not be kept in the dark and agencies such as the WHO and the U.N.'s Food and Agriculture Organisation (FAO), which jointly organised the experts' meeting, should release information as it became available.

"We'd rather that people eat a balanced and varied diet and moderate their consumption of fried and fatty foods," Arnold said, adding that this was long-standing WHO advice.