A 22-year-old Chinese woman who raised the alarm about a newborn trapped in a sewerage pipe kept quiet about being his mother, even as she watched the sensational two-hour rescue unfold.

The woman confessed to police a couple of days later when they asked her to undergo a medical check after searching her rented room, the state-run Zhejiang News website reported on Wednesday.

Firefighters were called on Saturday to the residential building in the Pujiang area of the eastern Zhejiang province city of Jinhua to rescue a baby trapped in the L-joint of a sewerage pipe just below a squat toilet in one of the building's public restrooms.

Video of the rescue was shown on Chinese news programs and websites and picked up worldwide, prompting both horror and an outpouring of charity on behalf of the baby.