WASHINGTON — Thirteen employees who worked the night shift at a nuclear waste burial site in New Mexico after an underground leak are carrying radioactive materials in their bodies, but it is too soon to say how much health risk this poses, Energy Department officials said on Thursday.

The workers inhaled plutonium and americium, which if lodged in the body bombards internal organs with subatomic particles for the rest of the person’s lifetime. The dose calculation is a bit arcane because the dose in such cases will be delivered over many years.

Calculating a lifetime dose will require several urine and fecal samples, taken over time, to determine the rate at which the body is eliminating the materials, said Joe Franco, manager of the Energy Department’s Carlsbad, N.M., field office, which oversees operations at the Waste Isolation Pilot Plant, where bomb wastes are buried in an ancient salt bed deep beneath the desert.

“Right now we have one single data point; there was one reading,” Mr. Franco said at a news conference in Carlsbad, explaining that more readings were necessary. Sensors in the salt mine detected a leak at about 11:30 p.m. on Feb. 14. At that hour, no one was in the mine, and automatic systems reduced the ventilation and ran the exhaust through high efficiency particulate filters, officials said, minimizing the flow of materials to the surface.