At least 13 people have been killed by a blazing fire that has engulfed a high-rise housing complex in Hong Kong, authorities said Wednesday, with others reportedly still trapped inside.

Fire Services Department Director Andy Yeung said a firefighter is among the dead. In a press release, Yeung said the 37-year-old had been a firefighter for nine years. “All of our colleagues are deeply saddened by the loss of such a devoted comrade,” he added. 

Nine people were declared dead at the scene and four others who were sent to the hospital were later confirmed dead, authorities told reporters. At least 15 more people were injured, and about 700 have been evacuated to temporary shelters.

The raging fire sent up a column of flames and thick smoke as it spread on bamboo scaffolding that had been set up around the exterior of the complex in the city’s Tai Po district. Live video from the scene showed firefighters aiming water at the intense flames from high up on ladder trucks as the dusk skies darkened, with smoke billowing from windows and red-hot embers falling to the ground.

It was not immediately known what caused the fire. Officials said the fire started at the external scaffolding of one of the buildings and later spread to inside the building and also to nearby blocks, likely aided by windy conditions.

The blaze was first reported in the mid-afternoon and has since been upgraded to a level 5 alarm, the highest level of severity, the Fire Services Department said.

Police have said they have received multiple reports of people trapped in the affected buildings. Records show the housing complex consisted of eight blocks with almost 2,000 apartments housing about 4,800 people.

Lo Hiu-fung, a Tai Po District Council member, told local TV station TVB earlier Wednesday that most of the residents trapped in the fire were believed to be elderly people.

“Nearby residents please stay indoors and close doors and windows and stay calm and avoid going to areas affected by fire incidents,” the Hong Kong Fire Services Department wrote on Facebook.

Tai Po is a suburban area in the northern part of Hong Kong and near the border with the mainland Chinese city of Shenzhen.