(AFP) The United States is working with the government to investigate a letter containing anthrax allegedly sent from here to a Microsoft office in Nevada, the US ambassador said today.

Both governments were concerned over the matter but it was "far too soon" to draw a conclusion as investigations were still in the preliminary stages, said ambassador Marie T Huhtala.

"I don't know what the outcome is going to be, but our governments are looking into it very carefully.

"However, if anthrax is deliberately sent through the mail it is a terrible act and obviously we condemn it. But with regard to what may have happened in Malaysia, it's far too soon to tell," she said.

Reports from the US said a letter containing a cheque, which had been sent by Microsoft to one of its vendors here, was returned to the Microsoft office in Carson City, Nevada, 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 several people were found to have been exposed to the rare disease recently. One of them has already died.

'Tampered sign'

Deputy police chief Mohd Jamil Johari was quoted by a local newspaper today as saying the letter arrived in Malaysia with "signs that it had been tampered with".

"While the letter was in this country, we received a report that there were signs it had been tampered with," he was quoted as saying by the Utusan Malaysia daily.

Mohd Jamil said the letter was sent back to the US after postal agencies here failed to find the location the letter was addressed to.

Prime Minister Dr Mahathir Mohamad has pledged full cooperation with the US in investigating the case and has urged them to provide details about the letter.