KARACHI, Pakistan, Feb. 1 (UPI) -- A letter laced with anthrax was sent to the home of Pakistan's prime minister, authorities said Wednesday.

"We have just received the lab reports confirming it was anthrax but we cannot say more than that at the moment," police officer Hakim Khan said.

The letter was sent to Prime Minister Yousuf Raza Gilani in October at his official residence in Karachi, Britain's The Daily Telegraph reported.

"We believe the culprit was a lady professor," said Akram Shaheedi, spokesman for Gilani.

The incident is the first case of the biological agent being used in an attack on a government office since a rash of letters filled with anthrax spores were sent to various agencies immediately after the Sept. 11, 2001, terror attacks in the United States, the Telegraph said.

Pakistani police arrested two men in November 2001 suspected of sending a letter containing anthrax to the country's largest newspaper, The Daily Jang.

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