There were conflicting reports about the cause of death. The Irrawaddy, a Web site dedicated to news about Myanmar, quoted family members saying Mr. Lo died of heart failure. But an officer with the country's special branch of the national police said the cause was a stroke.

From his humble beginnings in the hills of northern Myanmar bordering China, Mr. Lo rose to become what the administration of President Richard M. Nixon called the "kingpin of the heroin traffic in Southeast Asia." Mr. Lo used his drug profits to build a corporate empire under the name Asia World, a conglomerate that remains one of the largest in Myanmar today under the leadership of his son, Stephen Law.

Mr. Lo, who was of Chinese descent, commanded a militia of 3,000 men in the impoverished borderlands of northern Myanmar, where his soldiers guarded caravans of raw opium and multiple heroin refineries. The drugs were then sent to Thailand, where they were dispatched to global markets.

During Mr. Lo's years as a warlord in the 1960s and 1970s, heroin from Myanmar, then known as Burma, was widely trafficked across Europe and the United States.

Amid the decades of civil war in the country, the Burmese Army protected Mr. Lo's drug convoys in exchange for his support in the fight against Communist forces, according to the book "The Politics of Heroin," written by Alfred W. McCoy. But Mr. Lo switched sides in the early '70s, allying himself with rebels fighting for independence. Burmese forces pushed him across the border into Thailand, where he was arrested and extradited to Burma in 1973.

He was convicted of "rebellion against the state" and sentenced to death, which was commuted to life in prison. But he was released in 1980 under a general amnesty and began the second phase of his career, that of a leading business partner to the military junta that ruled Myanmar until two years ago.

Mr. Lo became instrumental as a liaison in the tangled politics of drug-financed ethnic armies that were — and still are — arrayed across northern Burma. He was reportedly able to continue his heroin business while serving as an emissary between ethnic-minority rebels and the central government, a role that pleased the dictators running Burma at the time.

U Khin Nyunt, a retired general and former prime minister who led peace talks with ethnic rebels, described Mr. Lo as an "important broker for peace talks."

"He was the first person to bring their messages — and deliver ours," Mr. Khin Nyunt said in an interview.

These government connections allowed Mr. Lo's business empire to thrive, and Asia World carried out countless construction projects for the junta. The United States government described Mr. Lo and his son, Mr. Law, as "key financial operatives of the Burmese regime."

In 2008, the United States Treasury, which described Mr. Lo as the "godfather of heroin," barred Americans from doing business with Mr. Lo and Mr. Law as part of wider economic sanctions against Myanmar's government. The sanctions were expanded to the family's broader network of companies in 2010.

The family's business empire even reached overseas; the American sanctions included 10 companies in Singapore owned by Cecilia Ng, Mr. Law's wife.

In the secretive world of Myanmar's elite, the extent of Mr. Lo's wealth is not known. But by one measure, it is vast. In an interview last year, a man often described as the richest person in Myanmar, U Tay Za, said the Lo family had surpassed him in wealth.

Wai Moe contributed reporting from Yangon, Myanmar.