The arrest came two days after he was charged with threatening to use a weapon of mass destruction.

Derek Brodie, 42, sent more than 200 letters, each containing a white sheet of paper with the word "anthrax" written vertically in multi-coloured block letters, according to the FBI. The letters were sent to government agencies, media personalities, actors and actresses and businesses.

"He had a habit of using the same rainbow-coloured pencil," said FBI Special Agent Steve Siegel. "He was sending these out to hundreds of people, various governmental agencies, media people, actresses."

None of the envelopes contained anthrax, the biological agent used in a series of unsolved 2001 mailings that killed five people. All were tested at a New Jersey Department of Health and Senior Services laboratory, Siegel said.

The mailings apparently began in May. Twenty of the letters were intercepted by US Postal Service employees in Freehold Township and Westfield in May and June, according to a complaint filed by Special Agent David Goldkopf.

One reached a hospital in Freehold on 7 June, prompting authorities to shut down its mail room and decontaminate workers as a precaution.

Investigation

Three days later, a letter carrier intercepted 19 more of the letters from an outgoing mailbox in Brodie's multi-unit building, and from that point on, more than 200 were intercepted, all with the same format, Goldkopf said. The one to Bush, addressed to "President Bush, Abilene, TX,: was found in the building's outgoing mailbox on 21 September, according to the complaint.

Interviewed by investigators last November, Brodie admitted sending the letter to Bush as well as 11 others found during a search of his apartment that also found coloured pencils, blank envelopes, a hole punch and papers, according to the complaint.

He also admitted sending letters to King Abdullah of Jordan and the Russian interior minister, Goldkopf said. Brodie, who was charged on Wednesday, was arrested without incident at his apartment by FBI agents, and investigators from the New Jersey state police and US Secret Service.

Mark Falk, a magistrate, later ordered him to be held without bail pending a psychiatric evaluation.