Florida authorities are investigating a threatening letter sent to Gov. Charlie Crist that contained a suspicious but nontoxic white powder.

Florida Department of Law Enforcement spokeswoman Heather Smith says the letter was intercepted Wednesday at the mail center at the state capitol.

Smith says investigators believe the letter was unrelated to one containing powder that was received at a John McCain office in Colorado on Thursday.

The letter sent to Crist was immediately sent to the Florida Department of Health for analysis, and preliminary results showed the substance wasn't harmful.

Smith says the law enforcement officials are satisfied Crist is safe and they believe the Florida investigation would be closed quickly.