BANGKOK — A Singapore Airlines flight hit severe turbulence over the Indian Ocean and descended 6,000 feet in a span of about three minutes, the carrier said Tuesday, leaving a British man dead and more than two dozen other passengers injured.

The flight was then diverted and landed in stormy weather in Bangkok.

Authorities said the 73-year-old British man may have suffered a heart attack, though that has not been confirmed. His name was not immediately released.

The Boeing 777 flight from London's Heathrow airport to Singapore, with 211 passengers and 18 crew members aboard, landed at Bangkok's Suvarnabhumi Airport, the airline said in a Facebook post.

Emergency medical crews rushed to help the passengers. Videos posted on the LINE messaging platform by Suvarnabhumi Airport showed a line of ambulances streaming to the scene.

Singapore Airlines said on Facebook that as of four hours after the emergency landing, 18 people remained hospitalized while another 12 were treated on outpatient basis. "The remaining passengers and crew are being examined and given treatment, where necessary,” it said.

Airports of Thailand group said the lightly injured and non-injured passengers are being assisted at a specially assigned location inside the terminal at the Suvarnabhumi Airport.

Thailand's Transport Minister Suriya Jungrungruangkit said Singapore would dispatch another plane later Tuesday night to transport the lightly injured and non-injured passengers to the city-state's Changi airport. He said that plane was expected to arrive in Bangkok at 9:45 p.m.

Kittipong Kittikachorn, general manager of Suvarnabhumi Airport, told a news conference on Tuesday night that the British man appeared to have suffered a heart attack.

Tracking data captured by FlightRadar24 and analyzed by The Associated Press show the Singapore Airlines flight SQ321 cruising at an altitude of 37,000 feet (11,300 meters).

At one point, the Boeing 777-300ER suddenly and sharply plummets to 31,000 feet (9,400 meters) over the span of some three minutes, the data shows. The aircraft then stayed at 31,000 feet (9,400 meters) for under 10 minutes before diverting and landing in Bangkok less than half an hour later.

The sharp descent in turbulence happened as the flight was over the Andaman Sea, near Myanmar. The aircraft sent a “squawk code” of 7700 at that time, an international emergency signal.

“Singapore Airlines offers its deepest condolences to the family of the deceased,” the airline said. “We are working with the local authorities in Thailand to provide the necessary medical assistance, and sending a team to Bangkok to provide any additional assistance needed."

Singapore Transport Minister Chee Hong Tat also extended condolences on his Facebook page. He said his ministry and Singapore's Foreign Ministry, as well as the country's Civil Aviation Authority and Changi Airport officials, along with airline staff, “are providing support to the affected passengers and their families.”