Bond for a convicted child molester suspected of being the "North Dallas Rapist" that terrorized the Dallas area more than 20 years ago has been increased to $500,000.

Robert Warterfield, 42, was living and working in Stephenville when Dallas authorities arrested him on Oct. 16, charging him with two counts of sexual assault against a child.

A Dallas County grand jury indicted Waterfield in October on two unsolved cases dating back to 1989 involving children who were 7 and 9 years old. In both cases, the assailant entered the children's bedroom windows, placed pillowcases over their heads, took them outside and sexually assaulted them, according to Dallas County District Attorney Craig Watkins. 

"The statute of limitations has not expired," Watkins said in a previous interview.

The string of assaults dates back to the late 1980s and early 90s, when dozens of young girls were sexually assaulted in the north Dallas area. In 1994, Warterfield pleaded guilty to assaulting a 15-year-old girl and was sentenced to 10 years probation.

Warterfield, who had been living on Mesquite Street in Stephenville and operating Dependable Yard Services, is classified as a "moderate" risk on the Stephenville Police Department's Sex Offender Registry.

He remains incarcerated in the Dallas County Jail.