A former cab driver serving more than 300 years in prison for kidnapping and sexually assaulting two young girls, one of whom he later admitted murdering, died Tuesday, California corrections officials said.

Curtis Dean Anderson, 46, had been receiving treatment at a Bakersfield hospital since Nov. 28, according to the California Department of Corrections and Rehabilitation. His death in the intensive care unit has been tentatively assigned to natural causes.

Anderson, an inmate at California State Prison, Corcoran since July 2001, was serving a 251-year sentence for kidnapping and sexually assaulting an 8-year-old Vallejo girl in 2000. The victim was shackled to the front seat of Anderson's car for two days and managed to escape by getting hold of the keys, flagging down a passing truck and diving through the open window.

Anderson later sentenced to another 50 years to life after pleading guilty to the 1999 kidnapping, molestation and murder of a 7-year-old girl. Xiana Fairchild disappeared while on her way to school in Vallejo, and her fate remained a mystery until her skull was discovered more than a year later in the Santa Cruz Mountains.