08/19/2014 04:44 EDT | Updated 10/19/2014 05:59 EDT

Growing list of class action lawsuits against Penn West Petroleum

CALGARY - The list of class-action lawsuits against Penn West Petroleum Ltd. (TSX:PWT) is continuing to grow, weeks after the Calgary-based crude explorer disclosed accounting irregularities.

Toronto law firm Rochon Genova LLP announced Tuesday that it had launched the latest claim against Penn West, noting in a news release that the company lost a fifth of its stock market value in the week after it announced the problems.

Ontario law firms Koskie Minsky LLP and Sutts, Strosberg are working together on a $400-million class action. And Calgary firm Docken Klym has filed an action to the Alberta Court of Queen's bench in conjunction with those two firms.

Another well-known Canadian law firm, Merchant Law, is also preparing a class action against Penn West.

Similar efforts are underway by a number of U.S. law firms.

None of the allegations against Penn West has been tested in court.

Last month, Penn West said an internal review going back more than four years had revealed hundreds of millions in improperly classified expenses. The issues were brought to light by chief financial officer David Dyck, who started on May 1.

So far Penn West has said it has to restate its financial results for 2012, 2013 and for the first quarter of 2014.