Reuters reports that there were also rumors among traders that Marfrig was continuing to build on its stake throughout the day, according to the local press.

In May, Marfrig announced publicly that it had bought 24% of BRF's outstanding shares, adding that it had no intention of influencing BRF's strategy or management.

Marfrig's decision to seek an antitrust review of its purchase of a stake in Sao Paulo-listed BRF, Brazil's biggest poultry processor and owner of leading brands like Sadia, underscores the sensitivity of the investment.

A Marfrig spokeswoman told Reuters on 1 June that the application, which is meant to be analyzed under a fast-track procedure, was made on 28 May and could be processed in as little as 30 days by Brazilian antitrust authorities.

The beef company said on 21 May that the investment, which comes almost two years after previous failed merger talks between the two companies, was a passive stake solely aimed at diversifying its holdings.

Marfrig, which spent around $800 million to build the BRF stake over a few days, said it had no immediate plans to seek representation on the company's board.

CADE said in an emailed message to Reuters that so far there was no notice of any filing in the federal gazette by Marfrig seeking antitrust clearance for the deal.

Also on Tuesday, Sao Paulo daily O Estado de S. Paulo and financial blog Brazil Journal reported that there were widespread rumors among traders of Marfrig building upon its position in BRF throughout the trading session.

Both companies declined to comment on the matter.

Common shares in BRF closed up 9.55%, the biggest gainer on Brazil's benchmark Bovespa equities index. Common shares in Marfrig closed up 0.6%.

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