(Adds media reports on negotiations, federal auditing court decision)
SAO PAULO, Oct 5 (Reuters) - Oi SA, Brazil's No. 4 wireless carrier, said in a securities filing on Wednesday that talks with U.S. activist hedge fund Elliott Management about an investment in the company took place but no firm proposal materialized.
Oi said in the filing that it was unaware of any further talks currently underway between the fund and the company.
Oi is in discussions with creditors to restructure 65.4 billion reais ($20.3 billion) of bank, bond and regulatory liabilities after filing for bankruptcy in June.
Wednesday's statement was a response to media reports saying the carrier had entered negotiations to receive investments of up to 10 billion reais from the U.S. hedge fund.
Rio de Janeiro-based Oi owes industry regulator Anatel and state lenders Banco do Brasil SA, Caixa Econômica Federal SA and BNDES a combined 20 billion reais, making the government its second-biggest creditor after bondholders.
On Wednesday evening, the federal auditing court (TCU) in Brasília made a preliminary ruling preventing Oi from entering into an agreement with telecoms regulator Anatel to convert about 10 billion reais of fines into investment commitments.
A representative for Oi had no immediate comment on the court ruling. ($1 = 3.2191 reais) (Reporting by Ana Mano; Editing by Daniel Flynn and Lisa Shumaker)