Bellevue Fire Department hazardous material technicians investigated an unknown white powder found in the mailroom of a Downtown Bellevue highrise on Monday morning.

The powder was discovered in the basement mailroom of the Symetra Financial Corporation on 108th Avenue Northeast early Sept. 26. Crews evacuated the basement and another floor while they investigated.

The powder was confirmed negative for biological components, but the substance is still unknown. Bellevue Police handled the powder after fire crews cleared it from the building.

A spokesman for the police said the powder was non-toxic, there are no charges, no crime was committed and there is no specific address related to the powder.

“As far as we’re concerned, the case is closed,” said Tory Mangione, stand-in public information officer for the Bellevue Police Department.

The person who handled the letter with the powdery substance is asymptomatic, said Bellevue Fire Department spokesperson Ryan Armstrong.

He said information was being gathered on those in proximity to the letter. Four patients were evaluated on the scene with minor abnormal symptoms. Armstrong said they were not being transported to the hospital as vital signs were stable.

Crews shut down 108th Avenue Northeast between Northeast 6th and Northeast 8th streets while they investigated.

This story will be updated as more information is made available.