OGDEN -- For those behind the latest apparent prank mailing of a mystery powder to a federal agency, the FBI is not done with you.
The investigation is continuing into the incident that prompted the April 28 evacuation of Ogden's James V. Hansen Federal Building, according to the FBI. The FBI is also investigating similar incidents a week earlier and last year in Farr West, as well as a mass mailing last year in three states.
In the most recent incident, 200 federal workers were sent home after an envelope addressed to the IRS office in the Hansen building was found to contain the mystery powder.
At the scene, 11 people were checked for symptoms and, as a precaution, underwent decontamination by firefighters in full hazardous-material gear.
The substance has been determined by testing to be nontoxic, said Debbie Dujanovic Bertram, spokeswoman for the FBI's Salt Lake City office, but the investigation is continuing. The agency will not be revealing what the substance was, she said, even to say if it was white, as in previous incidents.
But even if there was no actual threat in any of the incidents, criminal charges could follow, Bertram said.
"People need to understand this is not taken as a joke," she said. "We treat this as a criminal investigation. It's very important that people understand that.
"Look at the potential panic it causes, look at the response, all the resources deployed. We had call outs that day until late in the evening. We will stick to this. We're constantly developing new leads."
Bertram said the FBI is also seeking assistance in the investigations.
"We would ask members of the public, if they know anything, to contact the FBI at 801-579-1400," she said. "Ask for the on-duty agent."
As for the other incidents still under investigation, she said, "It's too soon to say whether there is or isn't a connection."
On April 22, a white powdery substance was found at an IRS building in Farr West. It turned out to be harmless, according to an FBI news release.
On March 1, 2010, the same facility in Farr West reported a possible hazardous substance found, described as a white powder. The FBI said all tests for hazardous materials and toxic substances in that instance were negative.
The suspicious white powder mailed to federal buildings in Washington, Utah and Idaho on June 14, 2010, was nonhazardous, FBI officials said at the time.
A Seattle FBI spokesman said the substance was "calcium carbonate, or chalk."
Receiving the white powder in mailings that day were the federal courthouse in Seattle; the FBI office in Spokane, Wash.; an IRS office in Bellevue, Wash.; the U.S. attorney's office and an FBI office in Coeur d'Alene, Idaho; the U.S. attorney's office in Boise, Idaho; and FBI offices in Salt Lake City and Pocatello, Idaho.