In the Netherlands, four people are appearing in court in connection with alleged attempts to trade in the deadly nerve gas sarin.
Specialist teams have spent Easter digging up a large area of woodland in the south of the country near Maastricht after conducting surveillance on a suspect. Nothing has been found.
The Mayor of Maastricht, Onno Hoes, said that the search operation was carried out without anyone being in danger.
The suspects – who are all Dutch, though one has dual Turkish nationality – were detained on suspicion of owning and concealing a lethal gas.
A police spokeswoman said they might have been trying to sell the sarin, though it was not clear if a buyer had been lined up.
Sarin nerve gas killed 13 people in an attack on the Tokyo underground in 1995.