Updated at 3.17pm: Census officers will re-visit 15,000 families in the next four weeks to verify information collected during the once-a-decade survey, the Census and Statistics Department announced on Friday.

As a follow-up to the survey completed on March 27, randomly-selected families will have to fill out a Post Enumeration Survey. Staff will visit these families from April 9 to May 4 between 9am and 10pm.

A department spokesman said: ''A random sample of quarters will be re-visited by regular field staff. Households and persons living in the selected quarters will be counted.''