Dutch authorities knew as far back as November that some eggs in the country were contaminated with an insecticide and they failed to notify their European partners at the time, Belgium's agriculture minister has said.

Dozens of producers in Belgium and the Netherlands are being investigated for eggs containing Fipronil, which is dangerous to human health.

Britain, France, Sweden and Switzerland have also been warned to keep an eye out for tainted eggs.

Belgium signalled on July 20 that it had found contamination.

Agriculture Minister Denis Ducarme said that Belgium's food safety agency has official documents "that indicated the presence of Fipronil in Dutch eggs as early as the end of November 2016".

Mr Ducarme told Belgian politicians that "there was concern over that lack of official communication from the Netherlands".

He said he wrote to his Dutch counterpart for an explanation, and also spoke to the European Commission's agriculture commissioner, "who seemed to already have this information".

Mr Ducarme also said that food safety controls have been boosted after contaminated eggs were discovered in Belgium last month.

Almost all eggs tested in Belgium have been found to contain very low levels of the insecticide.

One company tested on July 18 was found to have Fipronil levels well below the European limit. But the company demanded a second opinion, and the second test was above the maximum permitted.

The company has been quarantined since July 18, Mr Ducarme said.

It is believed that Fipronil got into the food chain when it was illegally added to a product used to treat poultry for lice and ticks.

An investigation is under way in Belgium and the Netherlands.