VIENNA (Reuters) - Tests show that some imported egg products in Austria have been contaminated with a potentially harmful insecticide, Austria's food safety agency said on Monday, adding to the list of countries affected by an international health scare.

Millions of chicken eggs have been pulled from European supermarket shelves as a result of the scare over the use of the insecticide fipronil, and hundreds of thousands of hens may be culled in the Netherlands.

"Fipronil was detected in a quarter of the samples," Austria's Agency for Health and Food Safety (AGES) said in a statement, adding that 80 samples had been taken from a range of products.

Contamination was found in wholesale products used in the restaurant industry that had come from Germany, the Netherlands, Belgium and Poland, AGES said, without elaborating.

The contaminated products would be withdrawn immediately, even though there was no public health risk, it said.

"The highest measure recorded was 0.1 milligrams (0.000003 oz) per kilogram (2.2 lb), or more than 10 times less than the highest measure recorded until now in Belgium," AGES said.

Some national regulators in Europe have voiced concern that many contaminated eggs have entered the food chain, mainly through processed products such as biscuits and cakes.

While a large amount of contaminated eggs would need to be eaten to show negative health effects, fipronil is considered moderately toxic and can cause organ damage in humans.

Fipronil is widely used to treat pets for ticks and fleas but its use in the food chain, for example to clean out barns, is forbidden in the European Union.

Germany received at least 28 million possibly contaminated eggs, nearly three times the number previously reported, the Neue Osnabrueckner Zeitung newspaper reported in Wednesday editions. It cited data obtained by the government of Lower Saxony from a European Union database.

Dutch authorities on Thursday arrested two directors of the company at the center of the food safety scare, with prosecutors saying they suspected them of threatening public health and possession of a prohibited pesticide.

Fresh eggs sold in Austria are mostly produced within the country, and the health ministry had said last week there was no indication that the Austrian poultry industry had been affected.

The first reports of suspected cases in Austria last week involved eggs that had been processed abroad and imported.

"There is no indication so far that fipronil was detected in Austrian products, especially in fresh Austrian eggs," health ministry official Ulrich Herzog told ORF radio.

Batches of possibly contaminated eggs from the Netherlands and Germany have been shipped to Sweden, Switzerland, France and Britain, EU filings showed earlier this month.

(Reporting by Francois Murphy and Alexandra Schwarz-Goerlich; Editing by Richard Balmforth/Alister Doyle/Ken Ferris)