Investigators find no further traces of anthrax

US investigators have found no further sign of anthrax in the office of a man killed by the disease since traces were found on his computer keyboard and in the nose of a co-worker, health officials said.

There have been no additional cases of contamination, Florida health department spokesman Tim O’Connor said.

Hundreds of people are waiting for test results to learn whether they were exposed to anthrax at the Boca Raton headquarters of supermarket tabloid publisher American Media.

Some worked closely with British-born Robert Stevens, a 63-year-old Sun editor who died of anthrax on Friday.

Investigators said anthrax bacteria were later found on his computer keyboard and in the nasal passages of mailroom employee Ernesto Blanco, 73. Mr Blanco was in good condition at an area hospital, Mr O’Connor said.

The source of the anthrax, which can be used as a biological weapon, is the subject of an investigation involving the FBI and the Centres for Disease Control and Prevention.

Federal authorities yesterday said they were awaiting test results to determine whether the strain of anthrax that killed Mr Stevens was manmade or natural.

Earlier yesterday, federal officials said they believed the bacteria was manmade, but they later said tests had not been completed by the Centres for Disease Control and Prevention.

The officials said investigators so far have found no evidence linking the Florida incident to terrorism, but they suspect it might have involved criminal activity.

The AMI building has been shut down as FBI crews dressed in white moon suits and black oxygen masks remove bags of evidence.

The bags were filled with plastic containers resembling Tupperware, and one contained what appeared to be a next-day air envelope.

‘‘We have in essence gone into the building, cleaned the building out, taken all samples as possible, and are following any trail - any possible trail,’’ President George W Bush said in Washington.

‘‘Thus far it looks like it’s a very isolated incident.’’

The case has sparked fear across parts of Florida. As of yesterday, the health department had tested 770 people with some link to the building in Boca Raton. It could take weeks for blood test results to come back.

Emergency officials also responded to calls around the state about suspicious powders being mailed or delivered to homes and businesses.

Firefighters in suburban Fort Lauderdale were quarantined for 12 hours, and officials closed a bank and law firm. Dozens of people were sent to hospitals for tests, but there were no reports of anyone becoming sick.

‘‘I could probably drop a package of Sweet n’ Low and evacuate this building,’’ Collier County Emergency Management Director Ken Pineau said.

Health officials have emphasised that there is no public health threat. Dr. Jean Malecki, director of the Palm Beach County Health Department, said anthrax tests at Mr Stevens’s home were negative

FBI spokeswoman Judy Orihuela also said there was no proof that a letter mailed to AMI several weeks ago was the source of the bacteria.

The love letter to singer Jennifer Lopez reportedly contained a soapy, powdery substance.

There was concern that another AMI employee had been exposed to anthrax. Martha Moffett, an American Media librarian, was treated for symptoms of pneumonia at a hospital, but was released last week after testing negative for anthrax. She has been retested twice.

In Temple Hills, Maryland, outside Washington, an armed man sprayed a substance into a subway station during a scuffle with police. Authorities took the man into custody and said it did not appear to be a terrorist act.

An Internal Revenue Service tax processing centre in Covington, Kentucky, was locked down yesterday after an employee reported receiving a letter that contained a white powder. Preliminary tests found no harmful substances, police said.