KAMPALA, Uganda — An American outdoors writer died of an apparent heatstroke while on assignment for Men’s Journal in a Ugandan jungle, the magazine said Tuesday.

Matthew Power, 39, had accompanied a British explorer, Levison Wood, while he tried to walk the length of the Nile River, the Men’s Journal website said. He died Monday a few hours after collapsing and losing consciousness, and his travel companions believe the cause of death was heatstroke, according to the magazine.

Asan Kasingye, the head of Interpol in Uganda, said his staff in northern Uganda reported early Monday that Power died suddenly after collapsing in the Ajai game reserve in northern Uganda. “I was informed that he just dropped dead on his own,” Kasingye said.

The U.S. Embassy in Uganda is helping to repatriate Power’s remains to Uganda’s capital, Kampala, where an autopsy will be performed, he said.