Texas may call out the National Guard in the hunt for a seven-inch radioactive rod used in drilling natural-gas wells, lost this week by Halliburton Co. (HAL) somewhere in a 130-mile swath of the state’s western oil fields.

The Texas Department of State Health Services said yesterday it sought help from an Austin-based National Guard unit that has equipment to locate the radioactive item, which can pose a health risk if touched or held for several days.

Halliburton lost the unit on Sept. 11, according to a report yesterday by the Nuclear Regulatory Commission. Pickup trucks with detection gear retraced the route of a vehicle that carried the radioactive rod before it was lost. The trucks drove at 10 miles an hour between Pecos, where the device was used on a well, and Odessa without finding the unit, the report said.

“It’s not something that produces radiation in an extremely dangerous form,” Chris Van Deusen, a spokesman for the health department, said in an interview. “But it’s best for people to stay back, 20 or 25 feet.”

Oil-field service companies lower the radioactive units into wells to let workers identify places to break apart rock for a drilling process known as hydraulic fracturing, or fracking, which frees trapped oil and natural gas. While the loss of such a probe occurs from time to time, it has been years since a device with americium-241/beryllium, the material in Halliburton’s device, was misplaced in Texas, Van Deusen said.

Loss of a device of this type hasn’t been reported to the NRC within at least the past five years, Maureen Conley, an agency spokeswoman, said in an interview. She said the material would have to be in someone’s physical possession for several hours for it to be considered harmful. The agency was notified because it works with states to regulate use of radioactive materials.

Halliburton called the Reeves County sheriff’s office in Pecos after discovering the item was missing, police sergeant Jerry Millan said.

“They told us they had lost a radioactive rod,” he said in an interview. “I’ve worked in the oil fields, so I knew what it was. We’ve been assisting with the search.”