Philadelphia police said they are seeking to recover a portable nuclear gauge that was reported stolen Friday.

The device was apparently stolen from the truck bed of a construction vehicle on the 500 block of Dickinson Street, although the complainant's truck had also recently been in the communities of Hatfield and Glenside in Montgomery County.

Police said the gauge contains small amounts of radioactive material and is used for measuring the density of soil at construction sites. It is enclosed in a bright-yellow case with an exterior decal of three triangular shapes surrounding a small circle -- the universal symbol for radioactive contents.

When the gauge is in its yellow plastic case (pictured above), it does not pose any threat or harm. The container should not be opened, however, because the device inside consists of a shielding container with a plunger-type handle protruding from the top.

As long as the source elements of the gauge are in the shielded position, the gauge does not present a hazard to the public, police said. But any attempt to tamper with the device or handle the source would subject the person doing so to potentially dangerous radioactive exposure.

A similar theft occurred in March 2007. In that case, the case was found and a piece of the device was missing, but it was later recovered.

Anyone with information about the device is asked to call 911.