In 2015, land mines killed or injured 3,233 people in 61 countries, according to the International Campaign to Ban Landmines—and 78% of those casualties were civilians. Buried explosives can remain armed and lethal long after wars end.

One key problem is detecting the mines, which can be slow, hazardous work. Current methods, which rely on metal detectors, X-rays and other legacy technologies, often require placing people or animals dangerously close to buried explosives.

Now scientists at Israel’s Hebrew University, reviving an American technology, have demonstrated a way of detecting land mines using genetically engineered bacteria and a laser-based scanner. The technique works, they say, without sending people, animals or even robots into harm’s way—and could eventually be extended to detect a host of different contaminants in a range of settings by tailoring bacteria as needed.

The technology, pioneered in the late 1990s at the Oak Ridge National Laboratory in Tennessee, hinges on the invisible vapors that land mines emit over time. Shimshon Belkin, one of the Israeli scientists, explains that land mines usually contain TNT, which gives off a degradation product called DNT. “DNT is the best signature chemical for explosives in general and land mines in particular,” says Dr. Belkin.

The Israeli scientists developed a version of E. coli that reacts to DNT in soil by producing a green, fluorescent protein. Although not visible to the naked eye, this fluorescence can be excited by a laser built into a scanning device that reports its findings to a computer. Best of all, the bacteria can be distributed without setting off any explosives, and the scanning can be done from a safe distance.