SAO PAULO, BRAZIL - Some prison officers began a 24-hour strike Thursday to protest the slaying of their colleague Nilton Celestino.

Sao Paulo Jail Guards Union (SINDASP) officials said the strike affected some of the 144 jails, inmate facilities and detention centers in Sao Paulo, Brazil's most populous state. The striking officers are those who serve meals to those inmates on 24-hour lockdown.

SINDASP also said they would stage another 24-hour strike if another prison officer was attacked.

Celestino, 41, who worked for more than ten years in the Itapecerica da Serra jail, was murdered Wednesday near his house.

Brazil's Federal Police is investigating whether the criminal gang First Capital Command (PCC) is behind the case.

The PCC threatened to launch a wave of attacks on police in Sao Paulo last month. Sao Paulo's police foiled three attacks against prison officers Monday, killing 13 PCC members.

Police said they were following the PCC members to prevent such cases.