At 1am on Friday, American businessman Stuart Mason began hearing cracking and popping sounds coming from outside at the Sheraton Hotel in Tsim Sha Tsui.

Mason looked out his window and was shocked to see burning debris falling from the sky, as flames engulfed a 48-storey scaffold-covered tower – only about 100 metres (328 feet) away from his hotel.

“I immediately grabbed my phone and ran down to see what happened,” he said. “I was nervous. The fire was really huge and I saw burning planks falling down. Groups of people were already on the street when I came down. They were either taking pictures or filming the fire.”

Police evacuated visitors and residents after the fire broke out at around 11pm on Thursday.

Mason was not the only one running when the under-construction skyscraper, which once housed the former Mariners’ Club, went up in flames. About 170 residents and tourists in neighbouring buildings were evacuated.

Among the people startled by the fire were guests at the Imperial Hotel, just a two-minute walk from the burning site.

“People were worried as they could hear the flying debris falling onto their windows,” the hotel manager said, who was off that night but was called in to help. “They asked if they needed to be evacuated. The lobby was just packed.”

He added firefighters and police had said no evacuation was needed as the 17-floor building was safe.

“They said it was safer to stay inside in case large debris fell down.”

Burning material and sparks were seen drifting around the area in Middle Road, the location of the construction site, and at one point threatened to spread to the five-star Sheraton Hotel and Hermes House, a nearby office block.

Living on the 10th floor of Far East Mansion, a building next to Hermes House, Somnath Rai said he remained vigilant since he first saw flying embers at about 11pm.

Firefighter investigate the structure on Friday.

“It was at first some small burning particles flying outside the window. Then I smelled something burning,” the 30-year-old accountant said. “When I looked out of the window, lots of smoke was engulfing that building. Then the fire alarm in my building rang.”

He was later told by a building manager that it was safe to stay inside.

Firefighters at the scene of a major blaze at an under-construction hotel in Tsim Sha Tsui.

“But I couldn’t fall asleep until 4am. I live alone. I have to be watchful,” he said as he was heading to work on Friday morning.

Firefighters managed to put out the blaze after nine hours. But as of 3pm, Middle Road was still partially blocked with only pedestrians allowed to walk by.

The green scaffolding over the skyscraper had disintegrated, while broken bamboo sticks were seen on the ground. Some of the floors of the building had turned black and debris was scattered on the ground.

Damage on the 48-storey tower in Tsim Sha Tsui.

Eight shops with entrances facing Middle Road were all closed on Friday, including the Sogo Department Store next to the Sheraton hotel and those in the Far East Mansion shopping arcade. The Tsim Sha Tsui Post Office, located on the ground floor next to the construction site, was also shut.

Only two hotels near the burning site, the Sheraton and the Imperial Hotel, operated as usual.

Zee Fok-cheong considered himself lucky as he was able to open his tailor-made shoe shop located inside the shopping arcade, which could be accessed through another entrance on the next street.

A resident walks past the scene of the fire on Friday.

“But I don’t think there will be any customers today,” he said, adding that it was hard to estimate how much business he would lose as the arcade was normally quiet on weekdays.

About 70 per cent of the stores inside the arcade were closed on Friday, according to a Post observation.

Authorities, meanwhile, are still checking the structural safety of the skyscraper and whether its scaffolding is at risk of collapse, while the cause of the fire remains unknown.

The blaze, which occurred at about 11.10pm on Thursday night, turned to a No 3 alarm fire 27 minutes later. It was further upgraded to a No 4 alarm on the one-to-five scale of seriousness at 1.46am on Friday.

Property developer the Empire Group is building a 42-storey Kimpton Hotel on the site. The company said it was working with government departments in their investigation.