SOUTH PORTLAND — Someone mailed an envelope containing white powder to the U.S. Citizenship and Immigration Service office on Gannett Drive, but the powder was tested and found to be harmless.

The powder leaked out of an envelope that was delivered to the office by the U.S. Postal Service on Monday, said Capt. Robb Couture, spokesman for the South Portland Fire Department. Someone at the front desk, who typically sorts the mail, noticed the substance. The fire department received the call about 1:20 p.m.

The fire department has equipment to test for the presence of biological, neurological and radioactive substances, and quickly determined that the powder was harmless, Couture said.

Two firefighters entered the building in protective suits and wearing self-contained breathing apparatus. They finished their work and declared the building clear about 3 p.m.

Couture said that in the past, during the post-9/11 era and the heightened alarm at the potential of a terrorist attack that followed, South Portland purchased costly testing equipment that helped them determine quickly that the powder found Monday afternoon was harmless.

Couture declined to discuss whether the envelope contained a note or any written message, and referred questions to federal authorities.