Shortly before 1:30 p.m., two inmates attempted to scale a inner perimeter recreational yard fence at the Reception Center Central Facility, said Lt. Dirk Williams, spokesman for the California Institute for Men in an email exchange.
Prison officials were able to stop the attempted escape, and the facility went into an immediate emergency prisoner count, officials said.
All inmates were accounted for, and the facility was rendered secure, Williams said.
Chino police authorities were contacted about the emergency count, police officials confirmed.
No injuries were reported during the incident.
The escape attempt comes only a few weeks after the state Department of Corrections and Rehabilitation announced its intention to possibly build a new Level II facility on the CIM property.
"It's a general threat to our public safety," said Mayor Dennis Yates in a recent interview over the proposed plan.
Level II inmates are the second lowest on the placement and security scale for state prisoners. A Level II facility primarily consists of open dormitories with a secure perimeter possibly patrolled by armed guards, according to the corrections agency.
Depending on available space, the state could build at CIM as many as three 792-bed units or a single facility with a second combining two 792-bed units.
At this week's City Council meeting authorized staffers to send a letter to the Corrections Department outlining their concerns.
The state will hold two meetings to discuss the expansion plan at 3 and 5 p.m. Jan. 30 at City Hall, 13220 Central Ave.
Reach Beatriz via email, call her at 909-386-3921, or find her on Twitter @IEBeatriz.