Police are warning British political figures to be on the lookout for hazardous packages that may have been sent by a Scottish separatist group.
The alarm has been raised following delivery of a parcel containing a caustic substance to 10 Downing Street, the official residence of Prime Minister Tony Blair.
Police say a second hazardous package was sent to an unidentified Scottish politician.
London police say bottles in the packages were labeled as eucalyptus oil, but they actually contained caustic soda, which can cause blindness and scarring.
British radio says the package sent to Downing Street was addressed to Mr. Blair's wife, Cherie. The Blairs are currently in Australia for the Commonwealth summit.
An anonymous caller has claimed responsibility for the mailings in the name of the little-known Scottish National Liberation Army. He told police a total of 16 packages were in the mail.
A British terrorism expert, Paul Wilkinson, says it could all be the work of a single individual.
"It's certainly within the capability of an individual to do this kind of thing. The organization Scottish National Liberation Army has in the past - when its been investigated been found to be very tiny indeed," he said.
The leader of the Scottish Nationalist Party, John Swinney, is calling the attacks "pathetic."
He said the perpetrators are not nationalists, but "they are criminals, plain and simple."