The Wilson Building was locked down this morning after an incident that resulted in a hazardous-materials cleanup.

From WTOP’s Mark Segraves:

D.C. fire department spokesman Alan Etter says a man walked into the lobby at city hall about 10 a.m.

He ended up in a confrontation with a security guard. During the confrontation, the man pulled out a bag containing a white powder and threw it at the guard.

It’s believed the man who threw the substance then ran from the building.

Etter told WTOP the department believes the substance is not harmful.