Brazilian police arrested former senator Gim Argello and launched raids in three states on Tuesday as part of a massive corruption investigation centered at state-run oil firm Petrobras, federal prosecutors said.
The 28th round of police raids in the so-called "Operation Car Wash" was based on evidence that Argello took bribes to ensure executives at major infrastructure companies would not be called to testify at a congressional committee in 2014, prosecutors said.
"These are alarming facts because they strongly suggest that a congressional investigative committee, which has an important role in our democracy, was used by a senator for corruption instead of fighting it," prosecutor Athayde Ribeiro Costa said in the statement.
The two-year investigation has uncovered systemic corruption across multiple companies, including state-run oil producer Petroleo Brasileiro SA , and the highest levels of government since the Workers' Party took power in 2003.
The probe has given powerful momentum to impeachment proceedings against President Dilma Rousseff, even though she herself is not being investigated.
Prosecutors said construction firms UTC Engenharia SA and OAS SA paid Argello 5 million ($1.44 million) and 350,000 reais ($100,519), respectively. Executives at those firms were arrested at earlier stages of the probe.
Other builders are being investigated, according to the statement.
Representatives at UTC and OAS did not respond immediately to requests for comment. OAS requested bankruptcy protection last year.
Dozens of executives from Brazil's top construction and engineering firms have been charged with bribery and money laundering, and about 50 politicians are being investigated for receiving kickbacks off contracts with Petrobras.
Tuesday's police raids took place in the states of Sao Paulo and Rio de Janeiro and in the federal district, according to a police statement. Potential crimes under investigation include corruption, money laundering and criminal association.