District police on Friday morning reopened all streets around the Canadian embassy, including two blocks of Pennsylvania Avenue between 4th and 6th streets NW, after determining that a suspicious substance in an envelope was benign, authorities said.

The streets were closed for about two hours as D.C. police from the Domestic Security Operations team, a unit within the Homeland Security Division that specializes in chemicals and hazardous materials, investigated the envelope.

Police were called to the embassy in the 500 block of Pennsylvania Ave. NW at about 8:50 a.m., said Officer Araz Alali, a D.C. police spokesman.

A U.S. Secret Service official said a substance was leaking out of a letter sent to the embassy. That official said the investigation has concluded and all embassy officials were allowed to return.

The embassy is located near The Mall and the National Gallery of Art, as well as several D.C. government buildings, including the U.S. and District courthouses and police headquarters.

This post has been updated.