The Dutch food and product safety board has stopped ‘dozens’ more poultry farms from sending their eggs to market because they may be contaminated with the pesticide fipronil.

Tests for traces of the pesticide, used to control lice in poultry, are now being carried out on eggs, hens and chicken manure at several dozen farms, the NVWA said in a statement.

On Monday, the NVWA shut down seven poultry farms after fipronil was found in samples of eggs. The chemical is primarily used as an insecticide, particularly to kill fleas, and is classed as a ‘moderately hazardous pesticide’ by the World Health Organisation. In the Netherlands it is banned in the poultry sector.

The NVWA, which took the action after a tip-off from the Belgian authorities, said in a statement there is no danger to human health. According to regional paper de Stentor, the contamination may have come from a pest control company in Gelderland which used the pesticide to deal with chicken lice.

The NVWA says it has not so far found concentrations of the chemical which would prove a direct danger to human health. However, continued consumption of eggs containing fipronil ‘could have damaging effects.’