A suspicious powder found in an envelope forced about 70 employees of The Des Moines Register to evacuate the building Friday for about four hours.
The powder caused no apparent harm, officials said.
The envelope, with a return address in West Virginia or Virginia, was opened in an office, according to the newspaper's Web site.
An accompanying letter included the message: ``To the Media: This is snail poison. We are no safer with Bush than before.''
Brian O'Keefe, a fire department spokesman, said the Secret Service had ruled out any threat to President Bush, who is scheduled to visit Des Moines on Monday.
A hazardous materials team sprayed affected areas of the newspaper's building with a bleach solution, photographed the letter and tested its contents for anthrax or ricin, a poison. O'Keefe said the initial tests showed no sign of the potentially deadly substances. A sample of the powder was sent to an Iowa City laboratory for testing.
Five of the evacuated workers, two men and three women, disrobed in tents set up outside the building, dropped their clothing in plastic bags and washed down with soap and warm water, O'Keefe said. They seemed to be doing fine late Friday, he said.
Meanwhile, a Tennessee man was charged Friday in Memphis with mailing bomb threats to schools in Florida, and investigators said he told of sending 25 envelopes filled with a white powder to mayors in the county.
The powder turned out to be flour.
Dane Ray Swindell, 46, was charged with mailing a false threat to damage or destroy a building by means of an explosive, the FBI said.
He was not charged with sending the powder, but the investigation was continuing, said FBI spokeswoman Judy Orihuela. She did not know whether Swindell had an attorney.