DALLAS (AP) — The FBI has released sketches and other information on a string of unsolved cold-case homicides that investigators say a serial killer admitted to carrying out.

The bureau updated on Wednesday information it had posted in November on its website. The update included drawings made recently by admitted serial killer Samuel Little, based on his memories of some of his victims.

An FBI statement says Little targeted "marginalized and vulnerable women who were often involved in prostitution and addicted to drugs." The bureau hopes the information will generate tips and clues from the public that could help solve the dozens of unsolved homicides.

The FBI says Little, who's 78, is in poor health and is expected to remain in a Texas prison.

The Texas Rangers say Little to date has confessed to 90 homicides nationwide over the past four decades. Ector County District Attorney Bobby Bland in Odessa, Texas, said 50 cold homicide cases have been closed as a result and most of the unsolved homicides remaining are in California.