NBC says it has ordered new seasons of its U.S. alternative series "The Biggest Loser," "Who Do You Think You Are?" and "The Sing-Off."

The announcement regarding the pickups for the 2011-2012 television season was made Tuesday by Bob Greenblatt, chairman of NBC Entertainment.

"Alternative series such as these three bona fide hits are important not only to their loyal audiences but also as strong components of the NBC schedule," Greenblatt said in a statement.

"They are each unique, attention-getting shows with terrific producing and talent auspices, and we're proud to be associated with them."