Russian rescuers scoured the sewer system in the central city of Bryansk on Monday in search for an 18-month baby who tumbled through the ground with his mother when the pavement suddenly collapsed.
The emergency service said the mother was walking her child in a stroller through the city's main square on Sunday afternoon when the pavement buckled because of a ruptured hotwater pipe.
The baby fell out of his stroller and vanished while the woman's policeman husband managed to pull her out of the four-square-metre (45-square-foot) hole using a rope.
The RIA Novosti news agency said nearly 70 rescuers had scoured several kilometres of the central sewer system in search for the baby without success. They were planning to employ special search robots later in the day.
Underground pipes carrying hot water occasionally burst in Russia because of extreme temperature swings that cause cracks in the system and release scalding steam that buckles the pavement above.