BANGKOK (AP) — Several of the more seriously injured people who were on the Singapore Airlines flight that hit severe turbulence earlier this week will need spinal surgery, a Bangkok hospital said Thursday.

Twenty people remained in intensive care and a 73-year-old British man died after the Boeing 777, which was flying from London’s Heathrow airport to Singapore on Tuesday, ran into bad turbulence over the Andaman Sea, hurling items and passengers and crew members around the cabin.

A public relations officer for Samitivej Srinakarin Hospital, where most of the 104 people hurt in the incident were treated, told The Associated Press that other local hospitals have been asked to lend their best specialists to assist in the treatments. He spoke on condition of anonymity under hospital policy.

Hospital director Adinun Kittiratanapaibool said at a news conference Thursday that none of the 20 patients in ICU were in life-threatening condition. They include six Britons, six Malaysians, three Australians, two Singaporeans and one person each from Hong Kong, New Zealand, and the Philippines.

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AP AUDIO: Several injured passengers on turbulence-hit Singapore flight need spinal surgery, hospital says

AP correspondent Karen Chammas reports many passengers on the Singapore Airlines flight from London to Singapore remain in a serious condition.

Passengers have described the “sheer terror” of the aircraft shuddering, loose items flying and injured people lying paralyzed on the floor of the plane.

It remains unclear what exactly caused the turbulence that sent the plane, which was carrying 211 passengers and 18 crew