A group of five overseas investors has acquired nearly 13 percent of Michael Baker Corp., according to a filing with the US Securities and Exchange Commission. The investors said in the filing they may seek to increase their stake in the future or even try to buy the company.

The investors, based in England and Bermuda, acquired roughly 1.1 million shares of Michael Baker, or 12.9 percent of the 8.3 million shares outstanding, for about $4.7 million, according to the SEC filing.

They said they bought the stake in Michael Baker, a Pittsburgh-area engineering and energy firm, because they view the company as fundamentally strong but undervalued.

Now, the investors are the second-largest group of Michael Baker shareholders. The company's employee stock ownership plan owns roughly 36 percent of the outstanding shares.

According to the SEC filing, which was submitted on Tuesday, the new investors include Acquisitor Holdings (Bermuda) Ltd., a Hamilton, Bermuda, company formed in 2002 to invest in strong but undervalued companies that have the potential to provide strong returns.

The remaining investors are based in London. According to the SEC filing, they include JO Hambro Capital Management Group Ltd., and a subsidiary, JO Hambro Capital Management Ltd., an investment management and advisory firm.

Also among the investors is American Opportunity Trust Plc, a publicly held investment trust company, and Christopher Harwood Bernard Mills, an individual with extensive relationships to the other parties.

The investors said in the SEC filing that they intent to have "open communications" with Michael Baker's leaders in order to monitor management's efforts to increase shareholder value.

Depending on developments ranging from Michael Baker's financial performance to the general state of the economy, the investors said they may take actions "as they deem appropriate" that could include putting proposal before other shareholders for a vote or attempting to replace existing directors of the company.