A portable gauge containing dangerous radioactive material fell off the back of a truck in West Virginia, and officials are offering a reward for the missing device.

The truck was transporting the device for the Pennsylvania firm Valley Quarries Inc. – a company licensed to possess and use the gauge. The company had been using the instrument in West Virginia at the time it was lost, and is desperately seeking to find it

Department of Environmental Protection officials said Tuesday that after one of its employees was taking a reading with the job, he placed the gauge in his pickup truck to drive to another site.

“Once he arrived, the gauge user realized the truck’s rear gate had opened and the device was missing,” DEP spokeswoman Lisa Kasianowitz told The Times Online. “Further, the gauge was not in its shipping container. The gauge user and a coworker promptly drove back along the route just traveled but were unable to find the device.”

Officials are now warning people to be on the lookout for a device that could pose dangerous health and contamination risks to the public.

“It is critical for anyone who has information about the lost nuclear gauge to contact the Pennsylvania DEP, Nuclear Regulatory Commission or a local law enforcement agency immediately. As long as the device is not tampered with or damaged, it presents no hazard to public safety,” the DEP Bureau of Radiation Protect David Allard said in a press release.

The nuclear density gauge contains radioactive material, which directs particles and counts those that are reflected or passed through material to measure density. In the construction industry, these gauges are used to create suitable soil environments to build roads and structures.

When left intact, the gauges are safe to handle. But anyone who tampers with them risks serious radioactive contamination and exposure.

Police are urging anyone who finds the gauge – which is bright yellow and the size of a shoebox – to call 911 or contact the Pennsylvania DEP. The gauge is a Troxler Model 3430 with serial number 32506. It contains about 8 millicuries of cesium-137 and 40 millicuries of americium-241. Cesium-137 is the principle source of radiation in the Chernobyl Exclusion Zone, which was designated for evacuation and placed under military control after the 1986 nuclear accident.

Valley Quarries is offering an unspecified reward for information leading to the return of their device. One of the company’s safety officer’s told the Nuclear Regulatory Commission that he saw someone stop along the road, pick up and drive off with a device that appeared to be a gauge.

Losing a nuclear gauge is no small matter, and generally triggers statewide police searches to find the missing device. In January 2010, Pennsylvania state police reported that a nuclear gauge disappeared from a facility in Coraopolis, and that tampering with it could release dangerous radioactive material. The company that owned the device offered a $1,000 reward to anyone providing information leading to its return. The gauge was recovered about a week later, after a road crew discovered the device on the side of a street.

In December 2010, a nuclear density gauge was stolen from a car in Bloomfield, Conn. The company that lost it offered a $500 reward for the return of the equipment. The device was eventually recovered, but police did not report how the company regained it.

Nuclear density gauges cost around $4,000 each and contain radioactive material that could pose risks to anyone that tampers with them.