DeKalb County Police Chief Louis Graham announced last week he was taking another look at four of the cases, and a fifth case was added Tuesday, the Atlanta Journal-Constitution reported.
Graham has also announced the formation of a five-member task force to look into the slayings.
Wayne Williams was convicted of two of the deaths in Atlanta in 1982 and sentenced to life in prison. After the trial, investigators said Williams killed the other 22 victims.
There were no trials, and the cases lay dormant.
Graham was a member of the task force that identified Williams, but he has insisted since then that Williams is innocent.
Graham became police chief in November, and now says he would open the five cases that occurred in suburban DeKalb County.
"These are DeKalb County cases. There has not been any finality to these cases," he said.