Firefighters said on Saturday that a fire that broke out at Choi Hung Road in the early hours of the morning started in a warehouse storing electronic parts, and that these fueled the fire and made rescue efforts difficult.

The fire department received the report at 5.17am. The blaze was brought under control after almost 10 hours, at about 3pm, and finally extinguished at 8pm

Chan Fu-shan, a commander from the fire department, added that firefighters also found the building's manual fire alarm system wasn't functioning properly.

"Many electronic parts and plastic casings were stored [at the site], which created a lot of smoke," Chan said. "The building was undergoing maintenance, so there is scaffolding and some protection nets on the external wall, which made the fire rescue and smoke dispersal more difficult."

He added that the electronic parts caused explosions and "flashbacks" that forced firefighters to retreat from the site, and that the fire was upgraded to a number 3 alarm at 8.53 am.

Seven people had to be evacuated by firefighters. One felt unwell and was sent to hospital.