Anthrax scare at Salt Lake City

There is a heavy security presence at the Olympics

With security concerns at the Winter Olympics running high, the airport at Salt Lake City raised the alarm on Tuesday night after an environmental sample falsely tested for anthrax.

Five people died from anthrax last year

When a new screening system detected the anthrax, and the result was apparently confirmed by a subsequent test, officials began implementing their emergency procedure.

But the samples, which were taken to a laboratory for more sophisticated testing, then tested negative four times.

The FBI had issued a warning that terrorist attacks may be perpetrated in the US or Yemen on or around 12 February.

There are more troops stationed in Salt Lake City for the Olympics than are currently on duty in Afghanistan

Public unaware

Utah Department of Health officials believe the false positive was not due to faulty equipment.

"These tests are extremely sensitive and we know that at the first level there is the possibility for a false result," said Scott Williams, the department's deputy director.

Airport operations were not interrupted during the alarm and the public were not informed until the scare was over.

There were 18 confirmed cases of anthrax infection in the United States last autumn, in which five people died.

No-one has been arrested.

The US Federal Aviation Administration now oversees airline security, but private companies will continue to handle security screening as the new federal work force is phased in.