"An agent saw the cat and went to look at it closely because something about it seemed wrong," Marcelo Avelino, the head of the prison guards' union, told the O Globo newspaper.

The agent found a bag tied to the animal's body filled with saw blades and drill parts for concrete drilling and digging tunnels, along with a cell phone complete with battery and charger, Avelino added.

The cat had often been seen coming in and out of the Alagoas jail.

Prison officer Luiz de Oliveira Souza told the G1 news website that prisoners had raised the cat and that relatives would often take it home after a prison visit.

"We were very surprised by this new tactic of prisoners," who trained the animal so that it returned to the prison and even managed to carry materials, the agent added.