Cassie Sainsbury's fiance has been turned away from seeing her in prison.

Accused cocaine smuggler Cassie Sainsbury’s fiance has been turned away from the Colombian prison where she is incarcerated as her mother and sister prepare to visit her on Mother’s Day.

Scott Broadbridge went to El Buen Pastor prison in Bogota on Saturday but was turned away despite the efforts of a fixer to gain authorisation for Mr Broadbridge to visit his 22-year-old fiance, News Corp reports.

Cassie Sainsbury and her boyfriend Scott Broadbridge. (Image via Facebook.)

Ms Sainsbury has been detained in Bogota since 5.8kg of cocaine was allegedly found hidden inside 18 headphone boxes in her suitcase at El Dorado International Airport in April.

She reportedly told a Colombian lawyer that she was tricked and given the headphones by a man she knew only as Angelo or Tom.

The man offered to buy her the headphones for a cheap price and brought them to her at the airport.

Ms Sainsbury's family maintains she is innocent and was set up.

Mr Broadbridge has previously told reporters he is certain his fiance is not involved in the drug trade.

Her mother Lisa Evans and sister Khala Sainsbury left Adelaide for Bogota on Wednesday.

It's expected they will visit Ms Sainsbury in prison on Sunday local time.

Why are we so obsessed with Cassie Sainsbury's story? Post continues below.

The 22-year-old is reportedly shocked her family have made a deal with Nine Network about her Colombian incarceration without asking her permission first.

In a telephone call from prison, Ms Sainsbury told News Corp she did not know her mother and sister had signed a deal with Nine Network's 60 Minutes program.

The pair reportedly asked for $1 million to exclusively sell their version of events, but it's unknown what figure they were paid.