STORY: British embassy staff were seen arriving at a Bangkok hospital on Wednesday to visit passengers who were still being treated for injuries after deadly turbulence hit their Singapore Airlines flight.

SQ321 was flying more than 220 passengers and crew from London to Singapore the day before, when it encountered severe turbulence.

A 73-year-old British passenger died of a suspected heart attack, and at least 30 people were injured, according to the airlines.

Though a Thai hospital said it was treating 71 people from the flight.

Dzafran Azmir was a passenger aboard the Boeing 777 flight, which was diverted to Bangkok.

"I saw people from across the aisle going completely horizontal, hitting the ceiling and landing back down in like really awkward positions. People, like, getting massive gashes in the head, concussions."

The 28-year-old student told Reuters that it happened so quickly, no one had time to respond.

He also said he had no idea how bad the situation was until the plane made its emergency landing.

"I didn't realize the things that broke within the airplane, the dents that were made in the overhead luggage compartments and all the additional kind of panelling above our heads. Like I thought it was just the oxygen masks coming out and then popping out the panel. But in fact, like heads had literally pushed through and broken plastic panels and like there was just there's blood and and there's bits and pieces just broken everywhere."

Azmir was among some 140 passengers and crew who finally arrived in Singapore on Wednesday, aboard a Singapore Airlines relief flight.

Company Chief Executive Goh Choon Phong said he was "deeply saddened" by the incident.

"We are very sorry for the traumatic experience that everyone onboard SQ321 went through."

According to Singapore's transport minister, the city-state's transport safety investigators have arrived in Bangkok, where the plane remains.

The minister said the U.S. transport safety officials were also being sent to support the probe, since the incident involved American planemaker Boeing.

It occurred over Myanmar's Irrawaddy Basin, about 10 hours into the flight, Singapore Airlines said.

Weather forecasting service AccuWeather said rapidly developing, explosive thunderstorms near its flight path most likely contributed to the violent turbulence.