Accused drug mule Cassie Sainsbury filmed smiling and dancing in Colombian prison

The first video of Cassandra Sainsbury behind bars in Colombia appear to show the accused drug smuggler in good spirits.

The 22-year-old South Australian is seen wearing blue jeans and a pink top, smiling and waving from a prison balcony.

She is seen standing on the enclosed area outside her cell in Bogota’s El Buen Pastor prison, in an area known as the Narco's Patio for its high number of inmates on drug charges.

Ms Sainsbury appears animated, smiling, dancing and waving to the cameras while talking to fellow inmates.

The images were captured when inmates were turned out of their cells while guards inspected them for drugs and contraband.

At one stage, she hands a fellow inmate a sign to hold up which says “Cassandra Pide Libertad Immediata” or “Cassandra asks for immediate release", as reported by The Courier Mail. There was another sign held up by the group translating as "Lithuanian foreigner died by negligence at INPEC [National Penitentiary Institute]".

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Ms Sainsbury has been in the custody of Colombian authorities since April 11, when she was intercepted at an airport and accused of trying to smuggle 5.8 kilograms of cocaine out of the country.

The 18 drug packages were allegedly concealed inside boxes of headphones.

Ms Sainsbury has maintained her innocence throughout the ordeal, claiming she bought the headphones as gifts from a man who promised her a cheap deal.

However, it has since been revealed that her movements in the lead-up to her Colombia visit gained the attention of the US Drug Enforcement Agency.

Security footage from the airport shows the moment Ms Sainsbury arrived to leave Colombia, but instead staff noticed a red flag on her passport and notified authorities.