An envelope found at Medford police headquarters was removed by a hazardous materials team this morning and is being analyzed at a lab, police said.

The envelope, which contained a brown granular substance, was found in the police clerk's office this morning, police Lt. Paul Covino said in a phone interview.

A device was used to measure whether it contained poison or explosives. It tested negative for both, Covino said. The State Police bomb squad was called to the scene.

The package was removed and taken to a state police lab for analysis, Covino said.