Gary Chan Sheung-han of the university's computer science and engineering department led the team behind the app.

Developed over the course of just two weeks and launched on the Google Play Store and Apple's App Store one month ago, the app uses data-mining techniques that organize and display Centre for Health Protection statistics to create a "heat map" of Covid cases.

The map marks buildings with confirmed cases during the prior 14-day period with a blue dot. In areas with a high number of cases, the buildings are marked along a spectrum of colors - blue is minimal risk, green is low risk, yellow denotes medium risk and red is high risk.

Users will also be notified if they are within 100 meters of a building with confirmed cases. The personal risk level of users can also be provided on a radar chart.

Chan said location information is only used in real-time and never stored on a remote server, adding: "User privacy is ensured."

The news came as authorities reported 4,376 Covid cases yesterday - comprising 4,180 locally-transmitted infections and 196 imported - and one death.

Also, 231 schools reported 287 cases, involving 230 students and 57 staff members.

In the wake of this, three schools announced weeklong class suspensions.

Further, more than 9,800 people originally under seven-day hotel quarantine were able to check out of their rooms early today following the shortened isolation policy.