A group of Pacific Exploration & Production Corp. shareholders is calling on Colombia’s financial regulator to block a takeover bid spearheaded by the oil company’s co-chairmen Serafino Iacono and Miguel de la Campa.

The group which includes Pacific’s largest shareholder, O’Hara Administration Co., updated a formal complaint with the regulator on Thursday, according to lawyer Jaime Granados. The original complaint had been filed last week.

An independent committee of directors, said to have selected the chairmen’s bid for control of the beleaguered company, isn’t really independent, with the whole process mired in a lack of transparency, Granados said in a telephone interview.

Pacific, in a response to questions from the regulator filed Friday, argued the committee was elected unanimously by the board and complies with rules to ensure its independence. The company declined to comment further. Colombia’s regulator didn’t immediately confirm the existence of the formal complaint.

A bid by Pacific’s co-chairmen is backed by Canadian private equity firm Catalyst Capital Group Inc., which is expected to provide about $500 million in funds secured against the company’s assets, according to people with knowledge of the matter. Current shareholders stand to lose everything under the deal, they said. Catalyst hasn’t confirmed it would back the bid.

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