Malaysia released 6,000 genetically modified mosquitoes into a local forest this month in an effort to curb dengue fever–dengue fever is transmitted by the female Aedes aegypti mosquito, is often found in tropical and subtropical environments, and causes headaches, muscular pain, and nausea, and sometimes death. There is no cure or vaccine and it’s not uncommon for travelers to pick up the disease, especially in the popular tourist countries of Southeast Asia.

The goal of the experiment, a first in all of Asia, is to reduce the number of offspring and lifetime expectancy of the mosquitoes, so that the mosquito population is ultimately reduced. The Aedes aegypti male mosquitoes were the ones released–genetically engineered in such a way to mate with females that don’t produce offspring and those that don’t live as long as others.

The experiment is far from accepted in local circles–several environmental groups protested the act and ultimately appealed to the government to not allow it to happen. But the government went ahead anyway and just announced this week that the experiment is now complete.

“I am surprised that they did this without prior announcement given the high level of concerns raised not just from the NGOs but also scientists and the local residents,” said Third World Network researcher, Lim Li Ching. “We don’t agree with this trial that has been conducted in such an untransparent way. There are many questions and not enough research has been done on the full consequences of this experiment.”

Concerns have been raised that the experiment could lead to an uncontrollable mosquito population but in fact they are designed to only live for a few days.