A West Australian grandmother and prominent Indigenous leader has been charged with importing almost two kilograms of an illegal stimulant into Japan, the country’s prosecutors say.

Donna Nelson has been held in Japan since flying into the country on January 4.

Her family say she was enticed onto an international trip by a romance scam and do not believe she would have knowingly been involved in drug trafficking.

An indictment filed to the Chiba prefecture district court states Ms Nelson took a suitcase containing approximately 1.9 kilograms of stimulants onboard a plane at Laos International Airport on January 3.

It says she then transited through Vietnam and took the suitcase onboard another plane bound for Japan.

She was allegedly then discovered by customs officials in Narita Airport, which is just outside Tokyo in the Chiba prefecture.

She is charged with the violation of the Stimulants Control Law and Customs Law.

Family says Donna Nelson was victim of scam

Ms Nelson’s family told the ABC last week they had not had direct contact with her since the day before her arrest, when she was in Laos.

They say the former Greens’ federal candidate was offered an all-expenses-paid trip to Japan by a man who she met on an online dating app, and whom she had been communicating online with for months.

They say they have been told by her lawyer that she was approached by a person claiming to be a business associate of the man she was travelling to meet, and he asked her to carry luggage to Japan.

They also say this was her first trip to Asia and she was not well travelled in non-English-speaking areas.

Ms Nelson was the chair of Derbarl Yerrigan Aboriginal Health service and ran a charity which received $1.65 million in federal funding in recent years.

She was relieved of the position of chair by Derbarl Yerrigan after her detention in Japan was made public.

The organisation said it needed to remove her because it could not carry out administrative functions without the chair.