A road materials testing device containing radioactive chemicals was stolen from a Virginia Department of Transportation trailer in Loudoun County last weekend, but officials said the gauge poses a threat to safety only if handled improperly.

Virginia State Police are investigating the theft, in which computer equipment and other articles also were taken. The testing device costs more than $2,000; officials said they had not yet determined the value of all the stolen items.

One or more thieves apparently broke through three locks to get to the testing device, a Troxler density moisture gauge described by police as bright orange, weighing 20 pounds and "about the size of a breadbox." If its contents -- Cesium-137 and Americium-241 -- were exposed, radiation from those chemical elements could harm someone standing within 20 feet, officials said.

But they said it would take extraordinary effort to remove the radioactive material from the testing device.

The gauge, used to measure the density of asphalt, stone, sand and other building materials, apparently was taken Friday night. It had been stored in a trailer used during construction of the 1.7-mile extension of the Route 7 bypass past the town of Round Hill. A ribbon-cutting ceremony for the road extension was held yesterday.

Officials said it might be hard for someone to sell the stolen device. "They probably have no idea what it's for," one state trooper said.

State Police spokeswoman Lucy Caldwell said thefts from highway construction sites are relatively common, but she said the Round Hill case "could be more" than routine larceny. She said fingerprints and other items of evidence were found at the site, but no arrests had been made by yesterday evening.