Brazil's securities commission CVM is looking into possible irregularities in the selling of shares in telecommunications firm Oi in 2014 and is investigating the alleged involvement of Banco BTG Pactual SA, Banco de Investimentos Credit Suisse (Brasil) SA, UBS Brasil Banco de Investimento SA, AZ Legan Participações SA and Ashmore Brasil Gestora de Recursos Ltda., Valor Econômico reported.

According to the publication, the regulator is looking into allegations that the companies were simultaneous short-selling Oi shares in trading sessions that preceded the date of the price fixing of the offer.

CVM alleges that pressure from short-selling investors caused a sharp fall in the value of Oi stock before its offering. The banks and firms in question have all denied any intentions to manipulate the market, the report noted.