Brazil's CADE anti-monopoly agency said Thursday it would launch an investigation into alleged collusion by 18 domestic and international companies on train and subway contracts awarded between 1998 and 2013.

The companies under investigation include France's Alstom, Canada's Bombardier, Spain's CAF, U.S.-based Caterpillar, Japan's Mitsui, Germany's Daimler and South Korea's Hyundai-Rotem.

The purported fraud affected more than a dozen projects valued at 9.4 billion reais ($4.03 billion), CADE's figures show.

The probe that triggered the opening of legal proceedings found that those multinationals and several Brazilian companies formed a cartel that pre-arranged the offers tendered in various bidding processes.

The alleged collusion occurred in the states of Sao Paulo, Rio de Janeiro, Minas Gerais, Rio Grande do Sul and the Federal District of Brasilia, CADE said.

The companies also purportedly bribed dozens of government officials for help in securing contracts in those states. EFE