SACRAMENTO, California — Hugo Pinell, a notorious California inmate whose 50 years behind bars included a violent escape attempt from San Quentin, was stabbed to death by two prisoners, sparking a brief but bloody riot at a prison near Sacramento, authorities said Thursday.

After Pinell was attacked Wednesday, as many as 70 prisoners began fighting in a 20-minute melee that sent 11 inmates to the hospital, one of whom remained in critical condition Thursday, the California Department of Corrections and Rehabilitation said.

A total of 29 inmates were injured, but no staff members were hurt, it said.

The motivation for the attack on Pinell is still under investigation, a spokeswoman said.

A native of Nicaragua, Pinell was initially sent to prison in 1965 for a rape in Marin County near San Francisco.

He made headlines as one of the so-called San Quentin Six after participating in a failed escape attempt in 1971 with Black Guerrilla Family prison gang founder George Jackson, which resulted in the deaths of three prison guards and three inmates, including Jackson.

At the time of his death, Pinell, 71, was serving six life sentences for murder, rape, battery, aggravated assault and voluntary manslaughter, the department said in a news release. Several of the crimes occurred while he was behind bars.

Pinell, who had been held in near-solitary confinement in the Security Housing Units at two of California’s toughest prisons for longer than any other inmate, was moved to the general population at California State Prison-Sacramento in 2014, after the state changed its policies for placement in those units.

Even though Pinell had gang ties, which led to confinement in the Security Housing Units, he had not recently displayed gang or criminal behavior and was moved out of the units, Terry Thornton, a spokeswoman for the corrections department, said.

The corrections department said it had recovered 15 inmate-made weapons after Wednesday’s violence. To quell the disturbance, correctional officers used “significant amounts of pepper spray,” and fired 160 rounds of nonlethal munitions, the department said.

It did not identify what munitions were used.

The prison is a maximum-security facility that houses about 2,300 inmates. Built in 1986 and sometimes referred to locally as “New Folsom” prison, it sits next door to Folsom State Prison, which is better known because of the song “Folsom Prison Blues” by Johnny Cash, who performed a celebrated concert there in 1968.