Partners of seven men arrested in connection with the discovery of the deadly toxin ricin in a London apartment may still be at large with more poison, police said today.

London's Metropolitan Police announced they had apprehended a seventh suspect in the case Tuesday and added that their inquiry was still active, with more arrests possible.

A spokesman said detectives were concerned that "there is a quantity [of ricin] out of our control which we are still looking for."

Police believe the suspects had intended to use the poison -- one of the world's most potent toxins -- to kill a small number of people in the hope of sowing panic among Britons.

The spokesman dismissed as speculation media reports that the men may have intended to assassinate a high-profile politician.

Police did not identify the seventh suspect, saying only that he was 33 years old and was being held at a London police station. They said the first six suspects were in their late teens, twenties and thirties and were of North African descent, but would not specify what country or countries they came from, declining to confirm media reports that the men were Algerian.

Police said nothing about the background of the seventh man. None of the seven have been charged. Investigators were questioning the suspects and continuing to search the north London apartment where the ricin was discovered.

British investigators are continuing to search a London apartment where traces of the toxin ricin were found.