Police have detained the treasurer of Brazil's governing Workers' Party in connection with a corruption scheme at oil giant Petrobras.

Joao Vaccari Neto and his sister-in-law were arrested at her home in Sao Paulo early Wednesday and are expected to be taken to the court in the southern city of Curitiba to testify.

Vaccari is being held "preventatively." He was charged last month with corruption and money laundering,

In a press news conference, federal police officer Igor Romario de Paula said officials have been collecting evidence against Vaccari.

Federal prosecutors have said the overall scheme involved the alleged payment of at least $800 million in bribes and other funds by construction firms in return for inflated contracts with Petrobras. Funds allegedly went to the Workers Party and other parties.