The magazine said its article was based on information from a U.S. delegation source at the United Nations biological weapons conference in Geneva that began last week. The attacks have killed five people.

"The U.S. delegation believe it is an inside job. ... Their members also have more information than has been made public," Kirsten Brodde, a reporter for the magazine, told Reuters. The magazine said: "It seems the attacker ... wanted to force through an increase in the budget for U.S. research on biological weapons."

It speculated that the attacker, who used anthrax-laced mail, had probably wanted to cause panic rather than kill anyone.

U.S. investigators have still not determined who was behind the attacks, but Attorney General John Ashcroft has signaled the authorities were inclined to believe they had a domestic source.

The attacks occurred in the aftermath of the Sep. 11 suicide plane attacks on New York and Washington and prompted initial accusations by President George W. Bush that Saudi-born militant Osama bin Laden may been responsible.

Asked about the magazine article, an FBI spokesman reiterated that investigators were pursuing a number of leads but no arrests appeared imminent.

A spokesman for the U.S. delegation in Geneva said he did not have any information about the article.

The magazine is linked to the environmental lobby group and shares its offices, but said it is financially and editorially independent.