Malaysian environmentalists are voicing concern over the government's experiment to use genetically modified mosquitoes to fight dengue fever.
The Malaysian government announced on Wednesday that it had released about 6,000 of the mosquitoes into a forest over the past 2 weeks.
Dengue fever spreads through female mosquitoes and can cause high fever and even death. No vaccine or treatment are currently available.
The genetically engineered male mosquitoes, which were developed jointly by the Malaysian government and a British firm, are designed to mate with females and produce to no offspring or ones with shorter lives, thus reducing the insects' population.
The government plans to examine how the mosquitoes adapt to the natural environment as well as practical applications.
In Malaysia, dengue fever has spread mostly in urban areas in recent years, killing 134 people in 2010 alone.
But environmentalists say the experiment could have unforeseen consequences, if a large number of the mosquitoes are released.