Lincoln Hazmat crews were dispatched to the Homeland Security Department offices after powder was found in an envelope Monday.
Just before 11:00 p.m., a worker discovered the powder when handling mail. According to LFR Battalion Chief Tim Linke, the worker then isolated the envelope in a bag and called authorities.
Health Department and Hazmat crews also responded to 850 S Street, where several agencies within Homeland Security function including the Immigration and Customs Enforcement offices.
Linke says several employees were asked to remain where they were inside the building, to keep from possibly being contaminated until the Health Department determined what the substance was.
According to Linke, Hazmat crews went inside to retrieve the bag and brought it to Health Department officials. Early tests of the powder were inconclusive, but a more extensive test shows the powder could be a kind of detergent.
Employees inside were cleared to leave the building around midnight.