A convicted murderer serving 70 years for a 1978 slaying near Houston who was also under investigation in the unsolved killings of 11 missing girls has died in a Texas prison.

Jeremy Desel, a spokesman for the Texas Department of Criminal Justice, said that inmate Edward Harold Bell, 79, collapsed Saturday at the Wallace Pack Unit in Navasota. The facility located about 60 miles (95 kilometers) northwest of Houston holds several elderly prisoners

"There did not appear to be any signs of foul play," Desel told The Associated Press on Monday.

Desel declined to discuss Bell's medical history, citing privacy laws. All in-custody deaths are investigated by the independent Office of Inspector General, according to Desel.

Bell's death leaves unanswered questions about the unsolved murders of 11 girls he claimed to have killed, the Houston Chronicle reported.

Bell was already serving time for killing Larry Dickens, an ex-Marine from Pasadena, when he admitted in 2011 to kidnapping and killing several girls who had disappeared from Galveston, Dickinson, Houston, Clear Lake and Alvin in the 1970s.

In one of several letters sent, Bell called the girls the "Eleven who went to Heaven." Bell acknowledged that he had also sent confession letters detailing several identical crimes to prosecutors in Galveston and Harris counties in 1998.

A few years after Bell made claims of being a serial killer, retired Galveston homicide detective Fred Paige and a Chronicle reporter collaborated to find evidence that he murdered the girls. The results of findings in that investigation were highlighted in a 2017 documentary on A&E called "The Eleven."

Galveston prosecutors then reopened the murder cases of Debbie Ackerman and Maria Johnson, the two island girls whose kidnapping and deaths Bell detailed in letters and interviews.

Bell was never charged with those two homicides, but he remained the key suspect until the time of his death. He also was the suspect in numerous other unresolved murders, but the departments spearheading the 11 cold cases could not find DNA evidence, nor were they able to locate weapons.

Rita Brestrup, who lost her sister Maria Johnson in 1971, said she had no words for Bell but was happy that he "no longer walks this earth and will never be paroled."

Bell was never prosecuted for any other murders besides Dickens, who was shot and killed after confronting Bell, a serial sex perpetrator who had exposed himself to a group of neighborhood girls.

Pasadena authorities subsequently arrested Bell and found murder weapons and pornography stashed in his pick-up truck. He made bail in Harris County and went on the run for 14 years.

After Bell was the subject of a 1992 Unsolved Mysteries episode, people provided tips which led to his arrest. The episode also featured Matthew McConaughey, who played Dickens in the actor's first TV role.

___

Information from: Houston Chronicle, http://www.houstonchronicle.com