Brazil's Federal Police agency said Friday it has begun legal proceedings against companies allegedly involved in a fraud scheme that has cost the public coffers almost $2 billion in unpaid fines and taxes.

It came a day after police said they had uncovered "criminal organizations" suspected of causing a shortfall of at least 6 billion reais ($1.9 billion) in unpaid taxes. Police said in a statement that the shortfall could be as high as 19 billion reais ($6 billion).

A federal police press officer said Friday that more than 50 companies in the industrial, financial and agricultural sectors are being investigated for allegedly bribing officials at the Finance Ministry's tax appeals court to reduce or annul fines on unpaid taxes. He spoke on condition of anonymity because he was not authorized to speak on the matter.

He would not name any of the companies being investigated.

The federal police statement said the investigation that began in 2013 found that officials of the tax appeals court leaked information to consulting and law firms in Brasilia, Sao Paulo and other cities to find companies interested in having their tax-court proceedings "facilitated."