Coahuila state authorities say the 44 police officers and four radio operators were put on two buses and driven from Ciudad Acuna to Saltillo.
Officials say they will be questioned over the weekend about possible involvement in the slaying of 25-year-old Jose Eduardo Moreira Rodriguez on Wednesday. He was the nephew of Coahuila Gov. Ruben Moreira and the son of former Gov. Humberto Moreira.
Investigators are considering as one possible motive that Moreira was slain in revenge for state police killing the nephew of a Mexican drug boss just hours earlier.