Prison officials believe an inmate used dental floss or a similar coated string to painstakingly cut his way out of his cell and kill a rival.

Antonio Lara was accused of crawling out from under his cell bars and killing Roland Rios, said Alfred M. "Mac" Stringfellow, Texas Board of Criminal Justice chairman.

Stringfellow said he didn't know how many steel bars Lara managed to cut through at the Coffield Unit of the Texas Department of Criminal Justice or how long it took.

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"He was very dedicated at doing this," Stringfellow told the Houston Chronicle in Tuesday's editions. "They are very resourceful people. That's all they have is time, so they can sit there and saw away until they finally are able to cut through it."

Lara, 26, was serving a 15-year sentence for attempted murder, robbery and aggravated assault. Rios, 41, was serving a 10-year term for aggravated robbery and injury to a child.

Stringfellow said Lara coated the nylon string with toothpaste or another abrasive in order to cut through metal bars and attack Rios as he was being escorted by guards to the shower March 16.

Rios' stabbing death resulted in confinement of some 122,000 Texas prison inmates to their cells in a rare systemwide lockdown to collect contraband and try and prevent further gang warfare.