A nuclear work tool disappeared from a parked truck in Riverside, prompting a theft investigation and a $750 reward for the device’s return.

The nuclear density gauge went missing June 3 at Campus View Drive and Mount Vernon Avenue, just north of Islander Park and less than a mile east of UC Riverside, city police say on their Facebook page.

The orange and yellow device weighs about 30 pounds and is carried in a similarly colored shipping container the size of a small trunk, bringing the total weight to about 90 pounds, according to the Facebook entry.

The manufacturer’s name — CPN — is printed on the outside of both the gauge and the shipping case.

A small amount of radioactive material is inside the tool, which workers used to inspect earthwork and paving construction projects, police say.

Properly used, the gauge poses no danger to operators or the public. But the theft raises concerns that it might be used — or tampered with — by someone unfamiliar with the device.

The tool is designed for use in civil engineering projects and construction to measure soil denisty or the water content of soil, accordig to the Office of Homeland Security website. The gadget also can be used for industrial, mining and scientific purposes.

Federal guidelines set security requirements for securing the device in vehicles.

In case of an accident, according to the Homeland Security website, an area 15 feet in all directions of the device should be cordoned off and the site must be kept under constant surveillance until emergency help arrives and radiation levels are known.

Anyone who has additional information about the missing device may call Detective Joe Miera at 951-353-7241.