Two Russian men were arrested earlier this year on suspicion of spying on a Swiss laboratory investigating the poisoning of Sergei Skripal, a newspaper investigation has claimed, BBC reports.
Swiss publication Tages Anzeiger and Dutch paper NRC said they were arrested in the Netherlands earlier this year.
The Swiss lab analysed samples from the poisoning of the former Russian double agent in the UK.
It has also dealt with suspected chemical weapons from the war in Syria.
The two men were expelled from The Netherlands shortly after their arrest, which had not been reported until now.
A spokeswoman for Swiss intelligence told the BBC that the agency had been actively involved in "the case of the Russian spies", without mentioning the laboratory at Spiez, near Bern.