Authorities in Colorado are alerting the public after radioactive equipment was stolen from a temporary construction site at a college campus and a reward is being offered for information leading to its return.

The Colorado Department of Public Health and Environment said that the portable moisture-density gauge containing sealed sources of radioactive material was discovered missing from the site at the Colorado School of Mines campus at 7:30 a.m. on Monday.

The gauge was stored in a metal container, which is yellow with Department of Transportation approved radioactive materials labels on it.

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The agency released images that are similar to the gauge and case reported stolen.

The stolen gauge contains small amounts of cesium-137 and americium-241, and is used to make measurements by projecting the radiation from the two radioactive sources into the ground and then providing a measurement on the top face of the instrument.

"As long as the radioactive sources are in the shielded position, the gauge would not present a hazard to the public," the agency states. "However, any attempt to tamper with the radioactive sources or handle unshielded sources outside their container could subject the person handling to radiation exposure."

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When the gauge isn't being used, the handle protruding from the top is normally locked with the source in the retracted, shielded position.

The company that was using the gauge at the time, Ninyo & Moore, is offering a reward of $500 for information leading to the safe return of the item.

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Anyone who may have seen or be in possession of the stolen gauge is asked to leave it alone and report its location to the Colorado School of Mines police at 303-384-2400, option 2; the Ninyo & Moore radiation safety officer at 303-579-2947; or Colorado Department of Public Health and Environment 24-hour radioactive materials response line at 303-877-9757.