(AFP) Police and health officials said today they are investigating reports that a letter returned to Microsoft in the United States from Malaysia contained traces of anthrax.

"We have to first establish if the letter actually arrived in Malaysia and whether it was tampered with here and then returned to the sender," said police spokesman Benjamin Hasbie.

The parliamentary secretary of the health ministry, S Sothinathan, said anthrax could not be obtained locally.

"If this allegation is true, we want to know where the deadly bacteria came from," he was quoted as saying by the Sunday Mail newspaper.

Reports from the US said a letter containing a cheque, which had been sent by Microsoft to one of its vendors in Malaysia, was inexplicably returned containing pornographic pictures.

It was tested and found positive for traces of anthrax, which has become a focus of bioterrorism fears in the US since four people were found to have been exposed to the rare disease recently. Two were infected, one of whom died.

Vice President Dick Cheney, while cautioning the anthrax investigation was still at an early stage, warned that suspected terrorist mastermind Osama bin Laden was known to have experimented with biological weapons.

"I think the only responsible thing for us to do is to proceed on the basis it could be linked," Cheney said.

DNA test

US officials said there were no immediate reported cases of anthrax infection stemming from the letter to the Microsoft office in Carson City, Nevada.

Nevada Governor Kenny Guinn said the risk to public health in the area remained very low.

The infected letter was sent to the Centers for Disease Control and Prevention in Atlanta, Georgia, to analyse the discovered strain of anthrax, according to the governor.

"We are asking them to perform a DNA test that we are not capable of, which will allow (authorities) to determine whether or not this is a strain with an organism that would carry the disease" or whether it is a vaccine strain, Guinn said.