ADDIS ABABA, Ethiopia — The police in Ethiopia said on Friday that the engineer who had been in charge of an enormous dam being built in the northwest of the country had taken his own life. The body of the engineer, Semegnew Bekele, was found slumped behind the wheel of his car in the capital, Addis Ababa, in July.

Mr. Semegnew had been the unofficial ambassador for the $4 billion Grand Ethiopian Renaissance Dam, which is expected to generate about 6,400 megawatts of hydroelectricity — more than double Ethiopia’s current production — and could earn the country hundreds of millions of dollars through energy exports.

Egypt has opposed the construction, saying it will cut into the already strained supply of water from the Nile, and the role of Mr. Semegnew had included trying to reassure Cairo that the dam posed no threat, as well as selling the project’s benefits to Ethiopian taxpayers, who were footing the bill.

A raft of conspiracy theories had sprung up around his death, with some speculating that he had become a target because he was going to expose corruption linked to the dam construction and others wondering whether Egypt had somehow played a role in his killing.