Pakistan PM's office reveals anthrax attack Updated at 10:37 a.m. ISLAMABAD - A university professor sent a packet containing anthrax to the office of Pakistan's prime minister in October last year, his spokesman said Wednesday, an attack with an unclear background in a country hosting extremists and battling them at the same time. No one was made ill by the toxin sent by the professor, and her motive was not clear, said Akram Shaheedi, a spokesman for the apparent target, Pakistani Prime Minister Yousuf Raza Gilani. Shaheedi said tests at laboratories run by Pakistan's Council for Scientific and Industrial Research in Islamabad since confirmed the substance in the package was anthrax. Shaheedi said the package was received in October 2011. He did not say why the case was publicized only now. Report: NATO says Pakistan aiding Taliban U.S. acknowledges CIA contact imprisoned in Pakistan U.S. enemies in Pakistan getting organized Islamabad police officer Hakim Khan said the prime minister's office informed the force of the incident a few days ago, and a criminal case was filed on Tuesday, a formal step in a police investigation. He said no arrests had been made yet. It was not known if the professor had links to any militant groups. Al Qaeda and other Islamist militants have carried out scores of gun and bomb attacks against the Pakistani state and Western targets in recent years, but have not been known to send letters or packages containing toxic material. Exposure to anthrax spores can be deadly, but preparing the bacteria in a form that can be easily delivered needs specialist knowledge and access to a laboratory. Al Qaeda is know to have experimented with toxic chemicals in the past, and U.S. officials have made protecting against "bioterrorism" a priority. Soon after the devastating Sept. 11, 2001, attacks in the United States, anthrax-laced letters were sent to media and government offices, including a leading U.S. Senator. Five people were killed and 17 others were made ill. The FBI announced in 2008 that a scientist at a U.S. army research institute was responsible, and the suspect killed himself as investigators closed in.