Reports from French Polynesia say the treasurer of the ruling Tahoeraa Huiraatira Party, Marcel Tuihani, has been detained to be questioned about the money transfers to the party's benefit.
Tahitipresse says this comes as part of an investigation centred on the jailed party leader, Gaston Flosse, who has been alleged to have been given money from a French advertising executive, Hubert Haddad.
The investigators want to establish whether the funds benefitted the party or Mr Flosse personally.
Earlier in the week, two former mistresses were asked to testify after leaked documents showed that the politician said he had used the money to pay them alimony.
This is in contrast to earlier claims that the executive sponsored his party because it stood up against pro-independence politicians.