Prison guards were said to have been surprised when they saw a white cat crossing the main gate of the prison, its body wrapped with tape.
A closer look showed the feline was also carrying drill bits, earphones, a memory card, batteries and a phone charger.
All 263 detainees at the prison of Arapiraca, a city of 215,000 people in the state of Alagoas, are considered suspects in the plot, which is being investigated by local police.
"It's tough to find out who's responsible for the action as the cat doesn't speak," a prison spokesperson told local paper Estado de S Paulo.
The cat was taken to an animal disease centre to receive medical care.
The incident took place on January 1, but was first reported by national media on Saturday.