A mysterious white powder caused the evacuation and temporary closure of a Flathead County building Thursday, but responders and health officials say the incident ultimately served as an effective training scenario.

Tests revealed that the substance contained nothing harmful.

It spilled out of an envelope in the Department of Motor Vehicles office on the third floor of the Earl Bennett Building Thursday at about 12:30 p.m.

The building was reopened by noon Friday and close to 100 employees returned to work.

Kalispell Fire Department Assistant Chief Dave Dedman said the Northwest Regional Hazardous Materials Team was sent to the scene on First Avenue West as a precaution. Field tests confirmed the powder posed no radiological threat, Dedman said, adding that biological tests were inconclusive.

“It was excellent training,” Dedman said. “Any time we get a call for service we take it very seriously.”

County Health Officer Joe Russell said there was less than one-eighth of a teaspoon of powder in the envelope. The substance was sent to Montana’s public health laboratory where results also returned “inconclusive,” Russell said.

He said the result was likely due to the fact that someone had attempted to clean up the powder with a disinfectant.

“There was nothing,” Russell said. “It didn’t appear to be any chemical. It had no smell and it didn’t appear to be a dangerous substance.”

Kalispell Police Chief Roger Nassett said investigators spoke with the person who sent the letter and determined there was no criminal wrongdoing. While the identity of the powder is still unknown, he said its possible it was construction-related residue.

The envelope also raised suspicion because it initially had been sent to Deer Lodge and had been repackaged and sent to Kalispell.

Like Dedman, Nassett said the incident acted as a training opportunity.

“These kind of things fortunately don’t happen often so it’s a good time for us to refine our processes,” Nassett said. “It’s a fine line between over-reacting and not doing enough.”

Those who had contact with the powder were decontaminated as a precaution, and no injuries or illnesses have been reported.

The powder garnered a response from Kalispell police and fire departments, Flathead County’s Sheriff’s Office, Flathead County’s Office of Emergency Services and the Federal Bureau of Investigation.