WASHINGTON, Oct 11: US authorities launched a criminal investigation Thursday after a third person was infected with anthrax but denied reports of a break-in at a government laboratory where the virus is stored.

“We do have the kind of investigation that investigates a criminal act,” US Attorney General John Ashcroft told NBC’s Today show.

Federal Bureau of Investigation agent Hector Pesquera said earlier, however, that “there is no indication at this time that this strain of anthrax was produced or created by people related to the September 11 incident.”

A media report Wednesday that a break-in at a government laboratory in Iowa where the anthrax virus was stored was vehemently denied.

“There was absolutely no evidence to indicate that the anthrax in Florida was stolen from any lab,” said Ashcroft.

A memorial service was held Wednesday for Robert Stevens, 63, a photo editor at the Sun tabloid, who died Friday after inhaling anthrax spores.

Ernesto Blanco, who worked in the mailroom of the Boca Raton, Florida-based American Media Incorporated (AMI), which publishes the Sun and other tabloids, has been in hospital undergoing treatment after a nasal swab concluded he too had been exposed to the deadly bacteria.

“He hopes to be out of hospital in approximately a week,” Blanco’s daughter-in-law, Mary Orth, told ABC television. “The antibiotics have kicked in and worked magnificently.”

The third case, a 35-year-old female AMI employee, is being treated with antibiotics that can halt infection in its early stages. Her exposure to the spores had yet to cause her any illness, said US Attorney Guy Lewis.

State Health Secretary John Agwunobi said a total of 700 tests had been administered to employes or visitors to the 6,000 square meter (64,500 square feet) headquarters of AMI and preliminary results were all negative.

So far investigators have found no link to the September 11 attacks but David Pecker, AMI’s chief executive, is convinced his firm is a victim of a terrorist attack.

“I feel that we had a bioterrorist attack here,” he told CNN late Wednesday.

Speaking on condition of anonymity, the source said the “unusual characteristics” of the bacteria pointed in that direction, although the Centers for Disease Control and Prevention (CDC) have yet to conclusively identify the spores as Ames anthrax, so named for the Iowa town where the laboratory is housed.

Bradley Perkins, a CDC anthrax expert from Atlanta, said laboratories are now “sub-typing the strains” of anthrax.

All three samples collected — from Stevens, Blanco and Stevens’ keyboard — matched.

“They appear to be from the same source,” Perkins said.

Dr Jill Trewhella of the Los Alamos National Laboratory in New Mexico told NBC Thursday that the lab has extensive information on the “geo-location” of organisms such as anthrax, allowing them to be tracked to a particular source.

“The particular strain reported ... (is) widely held in research labs,” she said, adding that strains held for research generally have had their virulence removed.

“We don’t have any ability to announce any source of the anthrax.”

Meanwhile, the appearance of packets of a mysterious white powder nationwide, including at the US State Department in Washington, have fed fear of a bioterrorist attack in the wake of September’s hijacked plane strikes that left some 5,500 dead.

WHITE HOUSE WORRIED: The US government is concerned about anthrax, White House spokesman Ari Fleischer said Thursday, after a third person was found to have been exposed to the deadly bacteria.