A device containing radioactive materials that disappeared from a construction site in central Fairfax County in June is still missing, a county police spokesman said last week.

"There has been no trace of the device," spokesman Warren Carmichael said. ". . . No sightings and no reports of any radioactivity."

The device, known as a Troxler soil moisture density gauge, is used by construction workers and road crews to measure the solidness of the ground. Its disappearance prompted warnings from federal officials that it could emit harmful levels of radiation if not handled properly.

The device, which resembles a large beige telephone and is about 15 inches long and nine inches wide, was reported missing to the Nuclear Regulatory Commission on June 16 after an employe of Alexandria-based ATEC Associates of Virginia left it unattended outside her car at an Oakton construction site. A police spokesman said ATEC officials told him the unidentified employe was fired.

In Virginia, Troxler gauges and those who operate them are licensed by the NRC. After an investigation, ATEC was fined $400 in August for violating NRC safety requirements by failing to control licensed material, according to Kenneth Clark, an NRC spokesman.

Clark said that to his knowledge there has never been a serious injury resulting from use of the radioactive devices. He said the fine was an attempt to emphasize the commission's safety requirements.

Clark said that about six of the devices, which cost about $5,000 and weigh about 25 pounds, are stolen every year. A few have been recovered, often found by a road, he said.