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Sheldon Adelson is opening his wallet once again, this time contributing at least $10 million to Mitt Romney's super PAC "Restore Our Future."

The Wall Street Journal first reported the haul and ABC News has confirmed the amount.

A Romney donor who is involved in fundraising for both the campaign and the superPAC said that Adelson gave two more contributions above the $10 million to the super PAC, but would not reveal the amount.

Restore Our Future would not confirm or comment on the donation.

"We don't comment on donors or donations or potential donors or donations," said ROF spokesperson Brittany Gross.

The billionaire casino mogul and his wife Miriam, who are worth more than $20 billion, gave $21 million to Newt Gingrich's super PAC. He met with Romney in Las Vegas last month as well as attending a fundraiser for him. Adelson was widely expected to donate to the presumptive GOP nominee's efforts at some point.

It's worth noting that Gingrich's superPAC "Winning Our Future", which Adelson bankrolled, levied sustained attacks against Romney during the GOP primaries. They were behind the "King of Bain" movie attacking Romney's career at investment firm Bain Capital and numerous television ads attacking the former Massachusetts governor.

The opposite also holds true. Restore Our Future's television ads, especially in Iowa, did serious damage to the candidate, pummeling Gingrich with attacks questioning his personal life and ethics violations while Speaker of the House.

This story has been updated since it was originally posted.