A suspicious letter containing white powder and a message claiming it was anthrax has prompted a lockdown at city offices in Pontiac, Michigan. The letter was mailed to Mayor Willie Payne's office. A spokeswoman said the letter was opened midday Wednesday, prompting officials to send eight people to a hospital for decontamination. Officials said the powder probably wasn't anthrax, which killed five people in a string of 2001 mailings. Pontiac police say the FBI is investigating. City offices are expected to remain closed Thursday.