German drugmaker Merck KGaA accused U.S. rival Merck & Co of hijacking its Facebook page and said it plans to sue to get it back.

Merck KGaA asked a New York judge to force Facebook Inc to turn over information to help determine how the German company lost the page, , and the ability to administer it.

According to a Monday filing with a New York state court in Manhattan, Merck KGaA contracted with Facebook in March 2010 for exclusive use of the page, but discovered last month that the unrelated Merck & Co was using it.

Facebook has not been cooperative in restoring the page, and in several alleged communications appeared nonresponsive or evasive in dealing with Merck KGaA, the filing said.

Because Facebook is an important marketing device, the page is of great value to Merck, and its misappropriation is causing harm to Merck, Merck KGaA said. It is not clear how that happened or who is at fault nor ... is Facebook providing clear information about what happened.

Merck KGaA said it may bring legal action alleging breach of contract and interference with its business. It did not indicate whom it may sue. Merck & Co is not a defendant.

Facebook spokesman Andrew Noyes and Merck & Co spokesman Ronald Rogers said their respective companies are looking into the matter. Merck KGaA declined to comment.

According to Merck KGaA, the Mercks became separate companies under the Treaty of Versailles, each owning rights to the Merck trademark in different geographic areas, as part of Germany's reparations following World War I.

Merck & Co is based in Whitehouse Station, New Jersey; Merck KGaA in Darmstadt, Germany; and Facebook in Palo Alto, California.

The case is Merck KGaA v. Facebook Inc, New York State Supreme Court, New York County, No. 113215/2011.

(Reporting by Jonathan Stempel in New York; Additional reporting by Ludwig Burger in Frankfurt; Editing by Lisa Von Ahn and Tim Dobbyn)