WASHINGTON - More US banks and the New York Times headquarters received letters with white powder on Wednesday, the Federal Bureau of Investigation (FBI) has said. FBI Spokesman Richard Kolko told reporters Wednesday that seven Chase Bank branches in Phoenix, Arizona and the New York Times headquarters in New York were among those that received envelopes containing the suspicious white powder. On Tuesday, at least 30 letters with the white powder have been mailed to banks in eight U.S. cities, despite preliminary tests finding them harmless. Since Monday, there have been 45 such letters delivered to financial institutions in at least 11 states. "Most of the letters contain a powder substance with a threatening communication," Kolko said, adding more tests are being conducted at regional laboratories. The New York Times said in a statement that an envelope containing white powder was found by an employee on the 13th floor of the company headquarters in midtown Manhattan in the morning, leading to the shutdown of part of the building's lobby. "People are able to get in and out of the building. The substance will be tested," said a spokeswoman for the newspaper. In Phoenix, the authorities said that so far no workers at the banks have been treated for any symptoms, and it was still early to tell whether the letters were related to previous ones. The series evoked the memory of the incidents in 2006 in which envelopes laced with anthrax were sent to media outlets and U.S. lawmakers, killing five people and shocking the nation that was still recovering from the Sept. 11 attacks.