Sources close to the inquiry have indicated that a Samoan man living in Australia is alleged to have been involved by sending money to two of the three suspects already charged.
The money had been spent in hiring a vehicle to carry out the plot, including the search for a weapon.
Last Friday the police say the evidence includes the use of social media from within and outside of Samoa.
"As we continue our investigation, we will explore other jurisdictions and determine whether nationals or entities were directly involved and where the evidence is confirmed, there will be further charges", the police said.
Meanwhile the three suspects who were charged last week will appear in court next Monday.