Brazil's justice ministry has started an investigation into the merger of telephony operators Oi and Brasil Telecom. The public inquiry was opened in the state of Rio Grande do Sul by federal prosecutor Jose Osmar Pumes. The probe will look at whether the merger constitutes the creation of a monopoly and if this could violate the country's universal service legislation. Oi and Brasil Telecom are awaiting the approval of the Brazilian regulatory authorities and for changes in Brazilian law to complete the deal. The takeover, first announced in April, is expected to create a national carrier that can better compete with foreign rivals such as Telefonica and America Movil.