The incident occurred around 11:30pm on Wednesday
The bodies were pulled from Karnaphuli River in Sharafbhata area of the upazila on Tuesday morning, said Rangunia police station OC Saiful Islam.
The dead have been identified as Tumpa Majumder, 30, and her son Bijoy Majumder, 5.
Police recovered the floating bodies after receiving news from the locals
in the morning, OC Saiful told bdnews24.com.
A picnic boat of the International Society for Krishna Consciousness capsized on the Karnaphuli River in Kaptai Upazila on Feb 14.
Rescuers managed to recover the body of Deblina, 10, on the same day but could not find the bodies of Tumpa and her son.