Captain Johannes Maheso said police divers and dogs searched the area within a five kilometre radius on Thursday.
“They had searched from a certain point of the Moretele river in Mamelodi, up until the Baviaanspoort prison in Kameeldrift,” Maheso said.
Neo Setlhabane, 10, Gomolemo Mangena, 10, and Bonolo Malemela, 9, were reported missing on Monday evening.
“They were last seen on Monday after school. They got home, changed into home clothes, and went to play,” Maheso said at the time.
“The children were playing near a church in the area. There is a stormwater drainage pipe which runs up to a river.”
Maheso said the river was about a kilometre away from the church.
Nothing was found in the pipe in which police suspected the children may have become stuck.
Police, search and rescue teams, and others have been searching for them since Monday.
Maheso said the search teams would go into the Moretele river if the water had subsided.
“It is currently full.”