By Lisandra Paraguassu and Ana Mano

SAO PAULO (Reuters) -Brazilian environment agency Ibama has notified 12 meatpacking plants, including two operated by JBS SA, for their alleged involvement in a scheme to buy cattle from illegally cleared land in the Amazon rainforest, according to a document seen by Reuters on Friday.

Ibama said in a statement on Thursday, without naming any parties, that 12 plants "are under investigation for acquiring suspicious cattle, triangulated with 'clean' farms, to disguise their illegal origin."

Ibama added that it had already fined six unnamed meatpackers in 4 million reais ($740,000) for "direct purchase of 8,172 head of cattle from embargoed areas."

JBS did not immediately respond to a request for comment.

Privately owned Frigol and Mercurio are also among the 12 implicated beef producers, the document showed.

Frigol said in a statement that Ibama had made a mistake, adding it had not bought cattle from the farm the agency said had been illegally razed.

Mercurio Chairman Lincoln Bueno told Reuters a third-party firm monitors the origin of the animals it processes, adding purchases are blocked from properties with environmental and labor irregularities.

As part of Ibama's investigation, the agency said it seized more than 7,000 head of cattle that were on 2,100 hectares of farms it had blocked from commercial use after illegal deforestation.

"Producing, selling or buying cattle from these embargoed areas is an environmental crime and those responsible are fined," Ibama's statement said.

In addition to seizing the cattle, Ibama said it fined the wrongdoers a total of 49 million reais ($9.04 million), without specifying if they were companies or persons.