Biological agent detectors tested in Boston subways

BOSTON (AP) - Boston's subway system is the site of a Homeland Security test to evaluate whether new sensors effectively detect biological agents.

Scientists will spray small quantities of a nontoxic virus in subway tunnels after hours to test the sensors.

The examination continues tests done since 2009 during which scientists released gases in the subway to determine how they travel through the system and identify where to place sensors.

This stage of testing began Aug. 29 at red line stations Davis, Harvard and Porter and will continue through next year.

The Environmental Protection Agency says the virus, Bacillus subtilis , doesn't cause disease and is considered nontoxic to humans, animals and plants.

Massachusetts Bay Transportation Authority Deputy Chief Lew Best says there is currently no specific bioterror threat to the Boston transit system.