Paul Manafort and Rick Gates, the two former high-ranking campaign aides to then-candidate Donald Trump, pose a "serious risk of flight" considering their massive wealth, overseas connections, and the possible prison time facing them, special counsel Robert Mueller writes in just-filed court papers.

Indictments against the two men were announced Monday by Mueller's office. They face money-laundering and other charges unrelated to the campaign.

"The defendants pose a risk of flight based on the serious nature of the charges, their history of deceptive and misleading conduct, the potentially significant sentences the defendants face, the strong evidence of guilt, their significant financial resources, and their foreign connections," Mueller wrote in a bail memo unsealed Tuesday and reported by NBC News.

"Both have had substantial overseas ties, including assets held abroad, significant foreign work connections, and significant travel abroad. Those aspects of the defendants' history and characteristics evidence a risk of flight."

The memo notes Manafort registered a phone and email account in March using an alias and took the phone on a trip to Mexico in June and to China and Ecuador in May. Manafort also has traveled to Dubai, Cancun, Panama City, Havana, Shanghai, Madrid, Tokyo, and Grand Cayman Island in the past year, according to the filing.

He and Gates both traveled to Cypress, where many of their foreign accounts are based.