At least 36 people are dead and nearly 300 others are missing as a massive fire continued to burn Wednesday at a high-rise apartment complex in Hong Kong’s Tai Po district, in the New Territories.

Firefighters said they are struggling to reach residents trapped on upper floors because the heat is too intense, though they vowed to keep trying. Officials confirmed they are in contact with some trapped residents, advising them to seal doors and windows to keep smoke out.

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The blaze has engulfed seven of the complex’s nine towers. The apartments were undergoing renovations at the time of the fire, with bamboo scaffolding and green mesh covering the buildings — material that may have accelerated the flames.

At least 33 people were injured in the fire, and more than 700 evacuated. The complex houses about 4,000 residents in roughly 1,900 flats.

Authorities have called it Hong Kong’s deadliest fire in nearly three decades. The cause remains under investigation.