The Mong Kok area, where the incident took place, is densely populated
Forty-six people were injured when two bottles of what's thought to be acid fell onto a busy street in Hong Kong.
Police suspect the bottles were dropped deliberately from a high-rise building, an official told a local newpaper.
Victims cried out as the liquid damaged skin and burned holes in clothing, witnesses said. Those taken to hospital were released the same day.
Police searched the building, but no arrests were made following the incident late on Saturday.
"After an initial investigation, we've determined two bottles containing a corrosive liquid were dropped from above," police spokeswoman Leona Leung told Reuters news agency.
She added that police had yet to determine the contents of the 750ml bottles and that samples had been sent for analysis.
Victims rushed away to get water to wash off the liquid, witnesses said.
A man who saw one of the bottles land told the South China Morning Post:
"It looked like an ordinary bottle of water, and the crowd began to disperse. Then I saw people with red faces and eyes in pain," he said.
The incident happened at about 1700 local (0900GMT) on Saturday in a crowded pedestrian zone in the Mong Kok area of Kowloon.