Jan. 20 in intensive care units after deadly turbulence aboard a Singapore Airlines flight, Bangkok officials say.

HONG KONG AND LONDON – Twenty passengers were being treated Wednesday in intensive care units at two Bangkok hospitals after a Singapore Airlines flight encountered severe turbulence, hospital officials said.

One person died on Tuesday when Singapore Airlines flight SQ 321 encountered “severe” turbulence, the airline said in a social media post on Tuesday. The Boeing 777-300ER departed London’s Heathrow Airport on Monday with 221 passengers and 18 crew members on board, according to the airline.

Bangkok hospital officials said in a statement issued today, Wednesday, that at least 85 people were transferred to three hospitals in Bangkok after the plane was diverted there. 19 others were treated at a local clinic, officials said.

The airline said late Tuesday night that four of the passengers were Americans. Two of them were injured.

Officials said 13 patients remained in the intensive care unit at Samitivej Srinakarin Hospital, along with seven at Samitivej Sukhumvit Hospital.

The statement said that 36 other passengers were receiving treatment on Wednesday in these two hospitals, along with two others in Bangkok Hospital. The statement said that by midday on Wednesday, 27 others had been discharged from the hospital.

Jeff Kitchen, a 73-year-old man from the United Kingdom, has died, according to authorities and the musical theater group he worked for. Singapore Airlines offered its condolences to Kitchen’s family, saying a permit On Tuesday, “our priority is to provide all possible assistance to all passengers and cabin crew on board.”

The flight, which was scheduled to arrive at Changi Airport in Singapore, landed in Thailand at around 3:45 pm local time, the company said.

ABC News’ Joe Simonetti contributed to this report.