(CNN) -- Now-aged serial killer Juan Corona was denied parole for the sixth time on Monday, California authorities said.
Corona, 77, is serving 25 concurrent terms of 25-years to life for 25 counts of first-degree murder in Corcoran State Prison in central California.
A parole board decided that "Corona's parole could reasonably pose a threat to public safety," said the statement from the California Department of Corrections and Rehabilitation.
He will not be eligible for another parole hearing for five years.
His crimes came to light in May 1971, when a farmer who had hired Corona as a labor contractor discovered a grave between two trees. Authorities went on to discover more graves in peach orchards along the Feather River near Marysville.
All of Corona's victims were men who were last seen with him or who'd been hired through his contracting business, according to the corrections department.