New Scotland Yard police headquarters is seen in London.

Seven people have been arrested on suspicion of financing terrorism overseas, British police said Tuesday.

Scotland Yard said the group was arrested as part of an operation that involved U.S. Homeland Security.

The operation is investigating a network suspected of illegally exporting khat, a leaf that can produce a mild high when chewed, from the U.K., where it is legal, to the U.S. and Canada, where it is a controlled substance.

British police said one woman and six men were arrested early Tuesday at four separate residences in London, Coventry and Cardiff, Wales.

Those four homes are being searched along with seven other residential addresses and a business address in Coventry, police added.

Police said the seven people arrested in the early morning raids are suspected of involvement in funding a terrorist organization and laundering the proceeds of crime for that purpose.

All of the suspects have been brought to a London police station for questioning. - Sapa-AP