According to AP, firefighters on Wednesday rescued hundreds of people who fled to the rooftop of a Hong Kong skyscraper and became trapped there after a major fire broke out. Hours later, the fire service said the blaze was extinguished.

The fire started in the early afternoon at the World Trade Centre on Gloucester Road in the city’s popular Causeway Bay shopping district, according to a government notice. The 38-story tower houses both offices and a mall.

Dense smoke was seen billowing out from the building, and photos and videos from those trapped inside showed poor visibility as smoke filled restaurants and stairways of the building.

Authorities said that the fire spread from the building’s bottom two floors, which is occupied by a mall undergoing extensive renovations.

The fire services system had been shut off in the mall area, according to fire department officer Ng.

“If the system is under repair, it’s possible that the contractor will shut down the area affected,” he said during a news conference Wednesday evening.

Authorities said they were still looking into whether fire safety regulations had been breached.

Earlier, police had told local media that about 300 people had evacuated to the top of the building while waiting to be rescued.

Preliminary investigations by the police suggested that the fire had broken out in the electrical switch room located on the first floor of the shopping mall, before spreading to the scaffolding that surrounded part of the building, according to local newspaper South China Morning Post.

Authorities said the fire was under control by around 3:06 p.m. and was largely put out by 4:30 p.m.

The fire services department deployed 176 firefighters to the site. Two breathing apparatus teams and two water jets were mobilized to help fight the blaze, police said.

In all, firefighters brought 770 people out of the building, said Ng Yau Sheung, Hong Kong Fire Services Department’s senior divisional officer. Another 40 people left on their own, he added.

At least 13 people were sent to hospital for treatment, according to authorities. Three of them suffered injuries while 10 others suffered from smoke inhalation.