In this latest case, one body was found on Saturday in a garage. Two others were found on Sunday - one in a backyard and the other in the basement of a vacant house. The three female bodies, all wrapped in plastic bags, were found about 182m apart, and authorities believed the victims were killed in the past six to 10 days.
Spotts said the suspect's comments had not provided clarity on whether more bodies might be found.
"He really hasn't stated that there's any more, but he hasn't said anything that would make us think that there's not," Spotts said.
Yesterday's search included 40 vacant houses. Authorities wanted to be thorough, the mayor said.
Cuyahoga County medical examiner Dr Thomas Gilson said the bodies were in advanced stages of decomposition and it would take several days to identify them and how they died.
Madison was classified as a sex offender in 2002 when he was sentenced to four years in prison for attempted rape, according to Cuyahoga County court records. He had previous convictions in 2000 and 2001 for drug-related charges.
One neighbour, Nathenia Crosby, said she knew Madison and had seen him walking through the neighbourhood. She said she had told him to stop chatting to her 19-year-old daughter.
"When I found out how old he was, I said, 'You need to move on, she's too young,"' Crosby said.
In May this year, a woman missing for a decade escaped from a run-down Cleveland home, saying she and two other women had been held captive there for years. Former school bus driver Ariel Castro was later charged with kidnapping, rape and other crimes.
He has pleaded not guilty.
- AP