The Belgian brewing company Interbrew says it has filed a criminal complaint over falsified documents saying it was to bid for South African Breweries (SAB).

The papers detailing a possible bid for SAB were leaked to the press last week, sending SAB's share price sharply higher.

Interbrew has now filed a criminal complaint at the Brussels Court of Justice over the documents.

It says internal documents were stolen and then altered to suggest a bid for SAB was imminent.

The company said in a statement that it was cooperating fully with authorities, but until the investigation is over it does not intend to comment further on the issue.

The UK's financial watchdog, the Financial Services Authority (FSA), has said it is to look into the case, but said there was no formal investigation underway.

Bid considered

Interbrew is the second largest brewer in the world by volume, and includes Stella Artois, Bass and Becks among its best known brands, while SAB is the world's fifth largest brewer.

When the papers were leaked last week, Interbrew admitted that it had considered the possibility of taking over SAB.

But the company said the briefing which was leaked was a "preliminary working document" which was part of a routine review of rival brewers, and had not been presented to directors.

The briefing had originally suggested a nil-premium merger, but the altered text had said a 30% premium should be paid.