Only between 64 and 74 Irrawady dolphins remain in the river between Cambodia and Laos, the World Wide Fund for Nature announced Wednesday.

Pollution from DDT, mercury and other toxins have led to a sharp decline in the rare species, with as many as 88 individuals dying since 2003, according to a recent report.

“These pollutants are widely distributed in the environment and so the source of this pollution may involve several countries through which the Mekong River flows”, said Verné Dove, report author and veterinarian with WWF Cambodia.

The organization is investigating the source of the contaminants, he said.

According to the international institution, high levels of mercury were found in some of the dead dolphins. Mercury, suspected to be from gold mining activities, directly affects the immune system, making the animals more susceptible to infectious disease.

WWF is working to conserve the species in Burma, Cambodia, China, Laos, Thailand and Vietnam.

Touch Sean Tana, secretary of state for the Council of Ministers and head of Cambodia's Commission to Conserve Mekong River Dolphins and Develop Ecotourism, denied the findings.

“Ninety-nine percent of the dolphins die because they are trapped in nets,” he said, denying that DDT and mercury were responsible.

“They want to cook their eggs, but they burn down our house,” he said of the WWF, adding that according to his estimates, 150 to 160 of the dolphins live in the Mekong between Cambodia and Laos.