The probe has uncovered corruption cases linked to people in several foreign countries.
"We expect the case load to double in volume, and the collaboration of Odebrecht and many of its executives will provide evidence that will lead to new investigations throughout Brazil," federal prosecutor Deltan Dallagnol said Thursday.
The probe that Dallagnol is leading, dubbed Operation Carwash, has netted scores of politicians and executives and put pressure on President Michel Temer as he tries to drag Latin America's biggest economy out of recession.
Those ensnared in the case include more than 100 politicians suspected of accepting bribes from powerful construction conglomerates for themselves or for their political party in exchange for allowing the builders to overcharge contracts with state oil giant Petrobras.
Current and former executives at Odebrecht have signed plea deals and agreed to cooperate with prosecutors in return for lighter sentences.
Dallagnol said that he and his team were surprised at the level of sophistication of the company's bribery scheme, dubbed the "department of bribery."
"We were surprised, because one thing is to know that... corruption is rooted, widespread and systematic in Brazil, and another thing is to look at the monster in the eyes," he told AFP.
"We are investigating thousands of crimes involving millions [of dollars] carried out by hundreds of people," Dallagnol, who is 37, told AFP.
The firm's former head Marcelo Odebrecht, who was sentenced to 19 years prison in March 2016, was reported last year to have given testimony implicating president Temer.
A key judge involved in taking testimony from Odebrecht executives, Teori Zavascki, died in a plane crash last week. Police are investigating.
Zavascki, 68, had been studying the confessions of 77 construction executives involved in the corruption scandal.
The judge's compilation of the confessions was to have been completed next month but will now likely be delayed.
Brazilian media have speculated that the testimony could implicate Temer.
The probe has uncovered corruption cases linked to people in several foreign countries, including the United States, Switzerland, Venezuela and Argentina.