British antiterrorist police have arrested six men for questioning after finding traces of a deadly toxin in a London residence.

Police say they acted on intelligence information to make the arrests of the six men, who range in age from teenagers to the 30s. The suspects' nationalities were not announced, but media reports say they are of North African origin.

Police say equipment and materials were confiscated when the men were arrested at residences in north and east London.

Chemical analysis found traces of ricin, a deadly toxin derived from the seeds of the castor plant.

British Prime Minister Tony Blair commented on the arrests after the police announcement. He said terrorists are actively seeking chemicals, toxins and other weapons to attack Britain.

"This issue is a real and active threat to our security, and I warn people, it is only a matter of time before terrorists get hold of it, and as the arrests that were made earlier today show, this danger is present and real and with us now, and its potential is huge," Mr. Blair said.

The police statement said Britain faces a range of terrorist threats from a number of different groups. It said the public should be alert but not alarmed, and it appealed for citizens to be vigilant and report anything suspicious to the police.