WASHINGTON (AFP) - Two campaign offices for Republican White House hopeful John McCain were evacuated after receiving a threatening letter containing a powder substance, a spokesman said Thursday. The first office to receive the letter threat was McCain campaign headquarters near Denver, Colorado, and the second was at a McCain office in Manchester, New Hampshire. "We have put all of our offices on highest alert. They're looking for anything suspicious and all staff has been quarantined as of right now," said McCain spokesman Jeff Sadofky on Fox news television, after the New Hampshire letter was found. "Immediately upon learning of this, federal and local law enforcement officials were notified," Sadofky said. "Staffs were immediately transported to a local hospital. Hazmat is on the scene and is looking for more information," he added, referring to a team trained to check for hazardous materials. "Our staff has evacuated as a precaution." Asked about the content of the letters, Sadofky said: "The best I can tell you is that the letters contained a threat to those who have read it. We have turned everything over to law enforcement."