By Rob Stein

Scientists have launched a major new phase in the testing of a controversial genetically modified organism: a mosquito designed to quickly spread a genetic mutation lethal to its own species, NPR has learned.

For the first time, researchers have begun large-scale releases of the engineered insects, into a high-security laboratory in Terni, Italy.

"This will really be a breakthrough experiment," says Ruth Mueller, an entomologist who runs the lab. "It's a historic moment."

The goal is to see if the mosquitoes could eventually provide a powerful new weapon to help eradicate malaria in Africa, where most cases occur.

"It's very exciting," Mueller says.

NPR was the only news organization allowed into the lab to witness the moment the releases began in early February.