More US mailbox bombs discovered

Authorities have urged people to be cautious

Another two pipe bombs have been found in a mailboxes in Nebraska and Colorado in the US, bringing to a total of 17 the number discovered since last Friday in three mid-western states.

Postal services have now resumed in the Midwest

The Nebraska bomb was found by a resident who had gone away for the weekend and returned to find the device, police said.

The authorities in Colorado warned residents to exercise "extreme caution" when opening their mailboxes after a pipe bomb was found in a mailbox in Salida, about 100 miles south-west of Colorado Spring.

If proved to be the same as those already found it may mean the bomber has broadened his campaign.

Crude devices

Postal workers in several mid-western states have returned to work wearing safety devices, and residents have been told to leave their post boxes open so that any device can be easily spotted.

Mailboxes are exploding! Why, you ask?... I'm obtaining your attention in the only way I can

Extract from note found with earlier bombs

The campaign began last Friday when six people were injured by explosive devices in the states of Iowa and Illinois.

Seven crude bombs - none of which exploded - were then discovered in the towns of Ohiowa, Columbus, Dannebrog, Davenport, Scotia and Seward. Officials said they had not been sent through the post, but placed there directly.

Four postal workers and two mailbox owners were injured in Friday's blasts.

Federal government officials described the bombings as "acts of domestic terrorism", and said notes had been found nearby warning of further "attention getters".

Special agent-in-charge from the FBI's Omaha office Wayne Dun said: "For the individual or individuals who may have been responsible for this: You have got our attention."

Home terror threat

In recent years the United States has been prone to bomb attacks carried out by its own citizens.

In 1998, Theodore Kaczynski, known as the Unabomber, was sentenced to four terms of life in prison without parole for a 17-year bombing spree which left three people dead and many injured.

Last June, Gulf War veteran Timothy McVeigh was executed for the 1995 bombing of a federal building in Oklahoma that killed 168 people and injured hundreds of others.

Following the 11 September attacks on the United States, the country was hit by a series of anthrax attacks, which the FBI believes was probably the work of a US national.