The tank from which liquid oxygen leaked at a civic-run hospital in Nashik, killing 22 COVID-19 patients, was operationalised just 21 days before the incident, an official said on Thursday.

The incident occurred on Wednesday afternoon when the patients, who were either on ventilator or oxygen support, suffocated to death after their oxygen supply stopped suddenly because of a malfunction in the main storage at Dr Zakir Hussain Hospital in Maharashtra''s Nashik city.