Campaign offices for John McCain evacuated in Centennial, Colorado and Manchester, New Hampshire, USA

The campaign offices for 2008 United States presidential candidate John McCain in Centennial, Colorado and Manchester, New Hampshire have been evacuated after receiving letter threats in the U.S. mail. Office staff state that the Centennial envelope contained an unknown white powder.

"We immediately notified local and federal law enforcement agencies and are looking to cooperate with them. 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 Jeff Sadosky, a spokesman for the McCain campaign.

There are currently no reports of injuries, but "staffs were immediately transported to a local hospital," added Sadosky. At least four people had to go through decontamination as a precaution. Authorities say that preliminary tests performed on the powder contained in the Centennial letter appears to be a protein and is not dangerous.

"We have not found anything hazardous in the initial testing, in the initial examination we did. We have no reports of anybody being sick," said Parker South Metro Fire Rescue Authority spokesman Andy Lyon who also said that authorities only found small granules of an alleged powder. The Manchester envelope was also given the all clear and no substance was found inside.

According to 9news.com, the letter in Centennial came from an unknown individual who is being held in Arapahoe County Jail. 9news.com describes the individual as a "prolific letter writer". The letter in Manchester contained a return address for Denver, but authorities say that the two incidents are not related.

The Democratic National Convention is set to begin in Denver in just four days.