Police are investigating the discovery of a radioactive device in the trunk of a car on Kings Highway in Fairfield, according to Fairfield police spokesman Lt. James Perez.

Kings Highway was shut down in the area of Villa Avenue while police responded to the scene. The highway reopened around 3 p.m.

Perez said the fire department was called to the scene to examine the device and measure its radioactivity. The Connecticut State Police Bomb Squad and Department of Energy and Environmental Protection also responded.

Police said the device in question is used to measure soil density.

According to a spokesperson for DEEP, the device – a Troxler gauge – is "used to monitor moisture levels in soils for construction projects." DEEP said the device was emitting a low level of radiation.

It's not clear how it ended up in the car or how the people in the car got a hold of it. Perez said the company to which it belongs was called to the scene to retrieve the device.

Officers served an outstanding arrest warrant to at least one person in the car, according to Perez.

No additional information was immediately available.

Check back for updates on this developing story.