In total, 144 Dutch poultry farms still remain closed because of the contaminated egg scandal, broadcaster RTL Nieuws said on Thursday.

At the height of the scare, 281 factory egg farms were closed down. The farms have been stopped from selling eggs and chicken meat because their products contain too much of the banned pesticide fipronil to be sold for human consumption.

A spokesman for the European Commission told a sitting of the European parliament’s agriculture committee on Thursday that contaminated eggs have been found in 22 countries within and outside the EU. Ukraine and Oman have imposed an import ban on eggs from the Netherlands, Germany, France and Belgium.

Meanwhile, it now transpires that the use of fipronil as a chicken de-lousing agent is more widespread than thought.

Romania

In Italy a consignment of eggs from Romania has been found to have 1.2 milligrams of fipronil per kilo, the highest concentration yet found. The legal limit is 0.72 milligrams.

The Dutch contamination originated at a small company called Chickfriend. Its owners are facing prosecution. According to broadcaster NOS, Chickfriend’s Belgian supplier bought the oils used as a delouser from a Romanian firm.

‘It would appear Romania is the source of the contamination,’ Hennie de Haan of the Dutch poultry farmers union told NOS. ‘But it is shocking to discover five weeks later that fipronil is being used in other EU countries.’

The EU’s rapid alert system has also recorded reports of fipronil-contaminated eggs which were produced in Italy, Hungary, Poland and Germany as well as Romania.