Seven terror suspects were arrested in England and Scotland during coordinated raids Thursday, police said, but the reasons for the arrests were not released.
Six men and one woman were arrested under the Terrorism Act 2000, police said. The act bans two dozen alleged international terror groups and makes it illegal to belong to or support the groups.
Lothian and Borders Police in Scotland, which led the operation, said the Scotland raids occurred in Glasgow and Edinburgh and the England raids in London and Manchester. Four people were arrested in Scotland and three in England.
"Although searches of the addresses are continuing it is important to stress that there has been no discovery of dangerous substances at this time," said Deputy Chief Constable Tom Wood, operations director of Lothian and Borders Police.
The suspects arrested in England will be taken to Scotland for questioning, police said.
Wood said he could not provide further details because the operation was linked to another case subject to a court gag order.
British police have carried out a series of raids since the Jan. 5 discovery of the deadly poison ricin in a north London apartment.
Ricin, derived from the castor bean plant, is one of the world's deadliest toxins and has been linked in the past to Al Qaeda and Iraq.
Since the Sept. 11 attacks in the United States, 270 people have been arrested in Britain under the Terrorism Act 2000. As of Jan. 24, 33 were on trial or about to be tried.