British police said on Friday that packages containing caustic soda had been sent to politicians including Prime Minister Tony Blair and that Scottish separatists had claimed responsibility.
Security screening at Downing Street discovered the corrosive chemical -- most commonly used for cleaning drains -- after detectives received a telephone warning from a little-known group of Scottish militants, dubbed the "tartan terrorists."
"Officers from the Metropolitan Police were alerted at approximately 2pm [yesterday] following a telephone warning from an anonymous male purporting to be from the Scottish National Liberation Army [SNLA]," a Scotland Yard spokeswoman said.
The man said a total of 16 parcels had been posted, police said, confirming that one had been intended for an unnamed Scottish member of parliament.
Postmarks on one of the packages suggested it had been posted in the western Scottish city of Glasgow, and police urged all politicians to be on the lookout for the remaining 14 parcels believed to still be in the postal system.
The contents of the parcels had been disguised as samples of eucalyptus aromatherapy products.
"We are urging people who may receive a package through the post in suspicious circumstances containing a liquid substance to contact 999 [emergency services] immediately," a spokeswoman said.
"Downing Street declined to comment, saying it was a matter of security, but a source said the parcel had posed no threat.
"The package was dealt with by the security procedures and there was no risk to any members of staff," the source said.
It is not the first time the SNLA, which seeks the creation of an independent Scottish republic and the restoration of the ancient Celtic language Gaelic as Scotland's national tongue, has hit the headlines.
A package purporting to contain the deadly bacterium anthrax was sent to St Andrews university in Scotland last August, shortly before Prince William, eldest son of heir to the throne Prince Charles started a degree course.
Shortly before the parcel -- which turned out to be harmless -- arrived at the university, the SNLA had reportedly said it would target the student prince during his four-year stay in Scotland.
In 1995, the group sent six letter bombs, including one to Blair's constituency home in northern England.