A Samoan opposition MP could be jailed if found guilty of treason for his role in a roadblock in Satapuala last week.
Villagers blocked the road between Apia and Faleolo in protest at plans to build a hospital on disputed land.
The Prime minister Tuila'epa Sa'ilele Malielegaoi has labelled the actions of protesters as terrorism.
He has asked the Attorney General to investigate the conduct of MP for the area Toesulusulu Cedric Schuster.
Our correspondent in Apia, Autagavaia Tipi Autagavaia says the MP is being investigated for not doing more to stop the protest.
"The Attorney General says the police are investigating the whole activity by the village of Satapuala which involves the Member of Parliament. And after the investigation the file will be referred to the Attorney General to consider charges."
The Attorney General was unsure how long the investigation would take.
Toesulusulu Cedric Schuster declined to comment on the investigation.