A prominent Indigenous community leader and Aboriginal health advocate has been arrested in Japan for alleged drug trafficking, after what her family says was two years of grooming by a "love scammer".

Ballardong Njaki-Njaki woman Donna Nelson is in custody but has not been charged with any offence.

On Tuesday Ms Nelson was chair of Derbarl Yerrigan, a health service for Aboriginal families, but has now been replaced.

Earlier this month drugs were allegedly found in a bag in Ms Nelson's possession at Narita airport near Tokyo.

Her family believe she was either tricked, or compelled, to carry a bag that was not part of her luggage when she left Australia.

On 4 January Ms Nelson stopped responding to messages from her family, leading to fears for her wellbeing. Three days later, through consular officials and Japanese police, they discovered she had been arrested, and have since only been able to communicate with her through her lawyer.

Her daughters told The Sydney Morning Herald and The Age the 56-year-old travelled to Japan to meet a Nigerian man known as "Kelly", who she had met two years earlier through an online dating site called AfroIntroductions.

They said Ms Nelson and Kelly had corresponded over a long period, discussing a potential trip to Brazil and making plans to get married in Nigeria in traditional African dress.

The family says Kelly sent Ms Nelson an image of a document he claimed was his Japanese residency card and offered to pay for some of her daughters to travel overseas, before convincing her to visit him in Japan and buying her business class tickets to fly to Tokyo via Singapore, Laos and Vietnam.

Her daughters believe that it was during a three-day stop in Laos that Ms Nelson met with an associate of Kelly and came to be in possession of the bag Japanese authorities found later at Narita airport.

Japan has a low prosecution rate but an extremely high conviction rate. Under Japanese law, people suspected of committing a crime can be detained for up to 23 days without charge while police investigate allegations. Suspects can be interviewed without a lawyer present, and bail is not available before charges are pressed.

Japan has severe penalties for drug-related offences, with prison terms of up to five years for possession and personal use, though suspended sentences can be applied in certain circumstances.

The UK Foreign Office notes that British nationals have received sentences for drug trafficking ranging from six to 17 years in Japan.

Ms Nelson, a well-respected community leader and health advocate, ran for the federal seat of Pearce as a Greens candidate in the 2022 election.

Her family said they want her experience to serve as a warning to other women searching for a partner online.

Department of Foreign Affairs and Trade officials have confirmed they are providing consular assistance to the family, but would not provide Fairfax Media further information for privacy reasons.

Ms Nelson's daughters said officials had visited her in detention to ensure she was in good health and offered after-hours support to the family.