Swiss authorities said Saturday that two people of Syrian origin had been arrested on suspicion of transporting "explosives and toxic gases" as part of a probe into a terror threat.
The two suspects arrested Friday are accused of the "manufacture, concealment and transport of explosives and toxic gases," the federal prosecutor's office said in a statement.
They are also under suspicion of violating Swiss law prohibiting "groups like Al Qaeda, Islamic State and similar organisations," it added.
Several Swiss media reported Friday that two people had been arrested in the Geneva region and that traces of explosives were found in their car, as the western city remained on alert due to an increased jihadist threat.
Geneva's public prosecutor has announced a news conference for later Saturday.
The Geneva region raised its alert level to three on a five-point scale on Thursday, and armed police were deployed at sensitive locations across the city, which is home to the UN's European headquarters.
The Le Temps daily on Friday cited an unnamed source close to the case as saying the Swiss had received a tip-off from US intelligence about a jihadist cell in Geneva.
Pictures of four individuals suspected of links to the Islamic State, which claimed the lethal Paris attacks, were published by media across the country.
Authorities in Geneva had said that the search for possible extremists was being conducted "in the context of the investigation following the Paris attacks."
But multiple sources, who requested anonymity, said there did not appear to be a direct link with the coordinated November 13 gun and suicide bombing attacks that left 130 dead in the French capital.
AFP contributed to this report.