French grandmother Cannabis smuggler Nantes Prison
A French grandmother tried to smuggle cannabis inside a detention centre in Nantes JEAN-SEBASTIEN EVRARD/AFP/Getty Images

A French grandmother was held by police after she was caught trying to smuggle a piece of cannabis resin inside the prison where her son is held.

The 77-year-old 'trafficker' was busted with the illicit substance in the visiting room of a detention facility in Nantes, northwestern France.

She was briefly questioned for possession and attempted trafficking of drugs and released shortly afterwards due to her old age and clean record, local paper Ouest-France reported.

Police and prison staff had been monitoring the visiting room as part of a crackdown on smuggling.

Three other detainees at the same jail were also reportedly found in possession of illicit substances.

The grandmother's identity was not released.