The vaping powerhouse Juul Labs replaced its chief executive with a veteran of Big Tobacco on Wednesday, deepening the company’s turmoil and raising doubts about the very future of the e-cigarette industry.

The sudden announcement capped a relentless cascade of events that has called into question the safety of devices once billed as a promising alternative to cigarettes, one of the world’s leading preventable causes of death. Now, Juul is looking to that very industry for its survival as it faces a federal criminal inquiry, new bans on some of its products, and an onslaught of state and federal regulatory investigations into its marketing practices.

Early Wednesday morning, after frantic days of internal meetings, the company announced that Kevin Burns would resign as chief executive. His chosen replacement is K.C. Crosthwaite , a top official at Altria, the cigarette giant that bought a 35-percent share in Juul for $12.8 billion last December and has seen the company it invested in rocked by growing crisis.

In another sign of regulatory and business uncertainty, Altria and Philip Morris International said on Wednesday that they had ended talks to merge, dashing the chances of reuniting the two arms of what had once been the tobacco giant Philip Morris.