March 4 (Reuters) - Former Brazilian President Luiz Inacio Lula da Silva was briefly detained for questioning on Friday in a two-year-long probe of a vast corruption scheme involving state oil company Petroleo Brasileiro SA, or Petrobras , a political crisis that threatens his successor, President Dilma Rousseff.
The following are some of the main events in the investigation:
March 20, 2014
Federal police arrest the former head of Petrobras' refining and supply department, Paulo Roberto Costa, the result of an investigation that started when they noticed Costa had been given a Range Rover car by convicted black market money changer Alberto Youssef.
Aug. 22, 2014
Costa signs a plea bargain deal with prosecutors, agreeing to explain the corruption scheme and name beneficiaries in exchange for a lighter sentence. Plea bargains become a cornerstone of the investigation.
Nov. 14, 2014
Federal police arrest 18 people, including former Petrobras engineering and services director Renato Duque and senior engineering executives, in the first broad raid of the investigation.
Dec. 11, 2014
Prosecutors in Curitiba formally charge 36 people, 22 of them from engineering firms OAS , Camargo Correa, UTC Engenharia, Galvao Engenharia, Mendes Junior and Engevix. Prosecutor Deltan Dallagnol declares war on corruption in Brazil in a nationally televised press conference.
Dec. 29, 2014
Petrobras bans 23 suppliers cited in the investigation from bidding on tenders. As of Dec. 2 2015, thirty-two firms had been banned.
Feb. 6, 2015
Aldir Bendine, former head of state-run Banco do Brasil SA, steps in as Petrobras chief executive after Maria das Graças Foster and other senior executives resign abruptly.
March 6, 2015
Brazil's Supreme Court says it will investigate the speakers of both houses of Congress and 32 other sitting politicians in connection with the Petrobras scheme.
April 15, 2016
Brazilian police arrest the treasurer of the ruling Workers' Party, João Vaccari, moving the investigation closer to Rousseff's inner circle. Vaccari resigns to focus on his defense.
April 28, 2015
After lawyers fiercely contest the legality of lengthy pre-trial jailings in Curitiba, the Supreme Court overrules federal judge Sergio Moro and orders nine executives to be released to house arrest.
May 26, 2015
Nestor Cervero, former international director of Petrobras, is sentenced to five years in jail for money laundering.
June 19, 2015
Brazilian police arrest the CEO of the country's largest construction company, Marcelo Odebrecht, head of family-run conglomerate Odebrecht SA. They also arrest Otavio Marques Azevedo, CEO of builder Andrade Gutierrez. Prosecutors said the companies may have led a cartel of engineering firms.
June 24, 2015
Police intercept a note from Marcelo Odebrecht to his lawyers asking to "destroy email." Odebrecht's lawyers say there was nothing criminal about his intent.
July 14, 2015
Federal police carry out search and seizure operations at the home of Senator and former President Fernando Collor de Mello, the first such operation targeting a sitting politician.
July 16, 2015
In a separate investigation, federal prosecutors open a formal inquiry into whether former President Luiz Inácio Lula da Silva improperly used his connections overseas to benefit Odebrecht after leaving office.
July 20, 2015
Three executives of Brazil's Camargo Correa group are convicted of money laundering, corruption and other charges, the first construction industry executives to be sentenced in the investigation. The CEO's sentence is reduced from 16 years in prison to a year of house arrest because of his plea deal.
July 28, 2015
Police arrest two executives involved in building a nuclear power plant for state-run utility Eletrobras. "Operation Radioactivity" focused on Eletrobras' Eletronuclear division, which is building a third nuclear-power reactor at Angra dos Reis, west of Rio de Janeiro.
July 29, 2015
Prosecutors say Renato Duque, former head of Petrobras' corporate services division, unfairly favored Italy's Saipem SpA on a contract for an undersea gas pipeline. More than a dozen foreign firms are thought to have bribed Petrobras executives, prosecutors said.
Aug. 3, 2015
Police arrest former government minister Jose Dirceu, one of the most senior members of the Workers' Party. Dirceu was Lula's chief of staff from 2003 to 2005.
Aug. 6, 2015
Prosecutors present formal charges against Jorge Zelada, the former head of Petrobras' international division, saying he favored U.S. company Vantage Drilling in a rig contract. Hsin Chi Su, chief executive of Taiwanese shipping firm TMT, was also charged.
Aug. 20, 2015
Prosecutors in Brasilia charge the speaker of Brazil's lower house of Congress, Eduardo Cunha, with taking a $5 million bribe related to two drillships contracts. Cunha, who broke with Rousseff's government, fiercely denies the accusations. Unspecified charges are made against Collor.
Aug. 21, 2015
Prosecutors say Camargo Corrêa agreed to pay 700 million reais to compensate state-run companies for damages related to bribery and price-fixing as part of a leniency agreement also signed with antitrust regulator CADE.
Sept. 30, 2015
Switzerland provides Brazilian prosecutors with Swiss bank accounts in Cunha's name.
Nov. 16, 2015
Prosecutors say they have evidence that bribes were paid as part of Petrobras' $1.2 billion purchase of Pasadena Refining Systems Inc in 2006.
Nov. 24, 2015
Police arrest Jose Carlos Bumlai, a powerful rancher and friend of Lula, bringing their investigation to the country's cane and agriculture sector.
Nov. 25, 2015
Police jail Senator Delcidio do Amaral and the chief executive of Brazil's biggest independent investment bank on suspicion of obstructing the investigation. The unprecedented arrests of Amaral, President Rousseff's point man in the Senate, and billionaire banker Andre Esteves, CEO of BTG Pactual SA , sent shockwaves through Brazil and paralyzed Congress.
Jan. 29, 2016
Prosecutors in Sao Paulo call Lula and his wife to testify in a money laundering investigation of beachfront apartments that may have been used as bribes. The testimony was later suspended.
Police say they have obtained a warrant to arrest campaign adviser João Santana. They also say they are investigating contracts with Petrobras, Sete Brasil, and Keppel Fels, the Brazil unit of Singapore's oil rig builder Keppel Corporation.
The magazine IstoE reports prominent ruling party Senator Delcidio Amaral, who was arrested in November, testified in a plea bargain that President Rousseff and Lula helped install widespread graft in the state oil company Petrobras and have repeatedly tried to thwart its investigation.
Police briefly detain former President Lula, family members and Workers' Party loyalists for questioning over the source of real estate assets and millions in payments suspected of coming from graft at Petrobras.
Compiled by Caroline Stauffer and Reese Ewing; editing by Grant McCool