Accused drug smuggler Cassie Sainsbury has reportedly reached a plea deal with Colombian authorities which could see her sentence cut from 20 years to 3¹⁄² years.

The Australian has reported that prosecutors in Colombia confirmed a deal in which the 22-year-old South Australian’s sentence would be radically reduced, in return for co-operating with authorities.

“There is a deal between Fiscalia (prosecution) and the prisoner which will be made public tomorrow,” a spokesman told The Australian.

It was reported earlier this week that prosecutors had encouraged Ms Sainsbury to provide details of all those involved in the alleged drug-smuggling enterprise.

The extent of her co-operation with Colombian authorities is unclear, but the former personal trainer will front court on Thursday where a judge will reportedly decide whether to accept the plea deal.

Ms Sainsbury who has spent more than three months in a Bogota prison after being caught trying to leave the country with 5.6 kilograms of cocaine hidden inside 18 boxes of headphones, was facing the prospect of more than 20 years in jail had she pleaded not guilty and gone to trial.

Cassie Sainsbury with the alleged drug haul at Bogota’s El Dorado airport. Photo: AAP

Ms Sainsbury and her family have offered varying explanations of the events, but consistently denied any knowledge of the drugs.

Ms Sainsbury repeatedly claimed she was given the headphones by a man who had been showing her around Bogota.

According to her original version of events, she had travelled to Colombia for work with a cleaning company.

She claimed at the time her uncle was the owner of the business before he sold the cleaning company to a mystery couple, known as Karen and June Dolshols, who paid for her trip to Colombia.

However, her uncle, Neil Sainsbury, told Channel 7 he had never owned a cleaning business.

Her father Stuart Sainsbury also cast doubt over his daughter’s original story, saying she and her fiancé Scott Broadbridge had planned her trip to Colombia since January this year.

This is in stark contrast to Ms Sainsbury’s first story, that it was a last-minute trip organised by the mysterious Dolshols.

Her Colombian-based lawyer, Orlando Herron, told Channel Nine’s 60 Minutes in May that Ms Sainsbury had admitted to trying to smuggle the cocaine into Australia, but had done so out of fear. She believed her family would be killed by an international drug syndicate if she refused.

Mr Herron told Nine that she had been naively lured by an advertisement on the website, Craigslist, that promised a loan and a trip to London. The ad allegedly did not mention any illegal activity.

Colombian authorities arrested Ms Sainsbury at Bogota’s El Dorado Airport in April after they were tipped off by US drug enforcement authorities. The US officials had been alerted about a last-minute ticket purchase for Ms Sainsbury by an unidentified person in Hong Kong.