Source:
https://scmp.com/article/364030/school-gas-leak-scareSchool in gas leak scare
Fourteen pupils and two teachers from Sha Tin Government Primary School received hospital treatment when they felt unwell after inhaling a bad smell, first thought to be a gas leak. Police and firemen helped to evacuate more than 1,000 pupils. Firemen later traced the smell to a water catchment being cleaned.