Lockdown at Santa Rita JailDUBLIN,
Calif. -- Violence erupted at the Santa Rita Jail in Dublin
Monday, and authorities to confine thousands of inmates to their cells.

Jail officials say they they were concerned about escalating tensions
after a fight broke out in the yard at one of the jails minimum
security units. As a result, they shut down the entire jail system --
minimum and maximum security units.

Alameda County Sheriff officials say the initial fight involved one
Latino and one black inmate. Authorities are investigating if it's
indicative of larger racial tensions inside the jail.

Nelson says it started as minimum security inmates in the yard were
getting ready for lunch. A deputy noticed that some of the inmates'
bagged lunches were gone. The deputy said if the lunches were not
returned, yard time would be revoked.

After their outdoor time was taken away, tempers flared and Nelson
says fists began to fly.

At least one inmate was seriously hurt and had to be taken to the

The lockdown was imposed for at least 24 hours. Officials expect it
to be lifted Tuesday afternoon.