Aug. 3 (Bloomberg) -- ``The Dark Knight,'' the sequel to ``Batman Begins,'' was the top film for a third weekend at U.S. and Canadian theaters, garnering $43.8 million in ticket sales and possibly challenging the all-time U.S. box-office record.

``The Mummy: Tomb of the Dragon Emperor,'' from Universal Pictures, opened in second place with $42.5 million, box-office tracker Media By Numbers LLC said today in an e-mailed statement. Walt Disney Co.'s ``Swing Vote'' debuted in sixth place with $6.3 million.

``Dark Knight'' may challenge the $600.8 million U.S. box- office record set in 1997 by Paramount Pictures' ``Titanic,'' researcher Box Office Mojo LLC said. In its first two weeks, ``Dark Knight'' has taken in more than twice the ticket sales as ``Titanic,'' which opened in a smaller number of theaters and gradually expanded.

``It certainly has a shot at $500 million,'' Media By Numbers President Paul Dergarabedian said in an interview. ``It's amazing we're even talking about it reaching the same numbers as `Titanic.' That's a decade-long record.''

The film -- with total sales at $394.9 million -- will likely reach $400 million in U.S. box-office sales in record time. ``Shrek 2,'' from DreamWorks Animation SKG Inc., achieved that milestone in 43 days and holds the record.

`The Mummy'

``Dark Knight'' helped Time Warner Inc.'s Warner Bros. vault to second place in 2008 sales from last among Hollywood's six major studios with $1.15 billion as of Aug. 1, according to Box Office Mojo.

In ``Dark Knight,'' Batman considers giving up crime- fighting as Gotham is terrorized by Heath Ledger's psychopathic Joker. Maggie Gyllenhaal plays Rachel Dawes, Batman's love interest. Morgan Freeman returns as Lucius Fox and Michael Caine reprises the role of Alfred, the butler. Ledger died in January of an accidental overdose of prescription drugs.

Brendan Fraser returns in ``The Mummy'' to fight the first Emperor of Quin, a shape-shifting entity cursed by a wizard centuries earlier who rises from the dead. The film opened in 3,760 theaters compared with 4,266 showing ``Dark Knight.''

Including ``The Scorpion King,'' the previous three ``Mummy'' movies ``have done very well and opened at No. 1 at the box office,'' Dergarabedian said. ``It's a family adventure movie and that pulls people into the theaters.''

`Swing Vote'

The Will Ferrell comedy ``Step Brothers'' fell to third place with $16.3 million for Sony Corp. The movie co-stars Ferrell and John C. Reilly as middle-age slackers, one living with his single mother and the other with his unmarried father. They are forced to share a house when the parents marry one another.

``Mamma Mia!,'' based on the Broadway musical, dropped to fourth place with sales of $13.1 million for distributor Universal. Set to the music of Abba, the film follows a young woman who invites to her wedding three men from her mother's past, one of whom may be her father. The movie stars Meryl Streep, Pierce Brosnan and Colin Firth. Universal is a unit of General Electric Co.

``Journey to the Center of the Earth,'' from Warner Bros., was fifth with $6.9 million in ticket sales. Brendan Fraser stars in the 3-D interpretation of the Jules Verne novel.

Sixth place's ``Swing Vote'' stars Kevin Costner in the story of a man whose vote will decide a U.S. presidential election. The film, which opened in 2,213 theaters, co-stars Kelsey Grammer, Dennis Hopper, Nathan Lane and Stanley Tucci.

`Wall-E'

Rounding out seventh through 10th place were Sony's ``Hancock,'' starring Will Smith, with $5.2 million; ``Wall-E,'' from Walt Disney's Pixar animation studio, with $4.7 million; ``The X-Files,'' from News Corp.'s Twentieth Century Fox, collected $3.4 million and ``Space Chimps,'' from News Corp.'s Fox, with $2.8 million.

Receipts for the top 12 movies fell 9.6 percent to $148.8 million from the year-earlier period, Encino, California-based Media By Numbers said. For the year, box-office sales are up less than 1 percent to $5.93 billion from the year-earlier period. Year-to-date attendance has dropped 2.78 percent from the prior period.

The following table has figures provided by studios to Media By Numbers. The amounts are based on gross ticket sales from Aug. 1, yesterday and estimates for today.

Movie                Rev.  Theaters  Wks   Avg./    Pct.  Total
                    (mln)                 Theater   Chg.  (mln)

1.  The Dark Knight  $43.8   4,266    3   $10,267   -42   394.9
2.  The Mummy         42.5   3,760    1    11,290    --    42.5
3.  Step Brothers     16.3   3,094    2     5,268   -47    63
4.  Mamma Mia!        13.1   3,062    3     4,285   -26    88
5.  Journey            6.9   2,285    4     3,009   -29    73.1
6.  Swing Vote         6.3   2,213    1     2,847    --     6.3
7.  Hancock            5.2   2,782    5     1,869   -37   216
8.  Wall-E             4.7   2,555    6     1,858   -26   204.2
9.  The X-Files        3.4   3,185    2     1,075   -66    17.1
10. Space Chimps       2.8   2,134    3     1,331   -37    22.1

To contact the reporter on this story: Andy Fixmer in Los Angeles at afixmer@bloomberg.net

Last Updated: August 3, 2008 15:34 EDT