Chinese searchers found on Wednesday one of two black boxes from a China Eastern Airlines plane that crashed this week in forest-clad mountains with 132 people onboard, the aviation regulator said.

The device was severely damaged, and it was not immediately clear if it was the flight data recorder or the cockpit voice recorder, an official of the Civil Aviation Administration of China (CAAC) told a media briefing.

Flight MU5735 was en route from the southwestern city of Kunming to Guangzhou on the coast on Monday when...