The deceased were Kulsum, 4, daughter of Nur Ali, and Tasim, 3, son of Kader Mandal of Ramdevpur village under Nayhata union of the upazila.
Locals said the children fell into the waterbody while playing alone on Saturday afternoon.
Locals rescued them and rushed to Upazila Health Complex where Tasim was declared dead.
As Kulsum’s condition worsened, he was shifted to Faridpur Medical College and Hospital where he breathed his last, reports UNB.
Officer-in-Charge of Mohammadpur police station Abdur Rahman said two unnatural death cases were filed in this connection.