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Three people with links to one of the San Bernardino attackers were arrested Thursday in a marriage fraud conspiracy, federal officials said.

The U.S. Attorney’s Office said that those arrested include the older brother and sister-in-law of shooter Syed Rizwan Farook. The third person arrested is the wife of Enrique Marquez Jr., an associate of Farook’s who has been charged for his alleged role in supporting the massacre.

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The three are not charged with terror-related offenses. The warrants relate to the questionable marriage between Mariya Chernykh, and Enrique Marquez in November 2014. Marquez has already been charged with a sham marriage. Prosecutors say they didn't live together and that she was paying him $200 a month.

The marriage allowed her to stay in the country.

Syed Farook and Tashfeen Malik arrive in Chicago on July 27, 2014. U.S. Government

According to the U.S. Attorney's California office, the three people with family connections to Syed Rizwan Farook, one of the shooters in the deadly terrorist attack at the San Bernardino Inland Regional Center in December were arrested this morning on federal conspiracy, marriage fraud and false statement charges.

“This is the latest step in the comprehensive investigation into the horrific attacks in San Bernardino last year that took the lives of 14 innocent Americans and deeply affected so many more,” U.S. Attorney Eileen M. Decker said in a statement.

In December, a grand jury indicted Marquez was charged with conspiring with Syed Farook to plan terror attacks in 2011 and 2012, years before Farook and his wife, Tashfeen Malik, opened fire at the Inland Resource Center in San Bernardino on Dec.2.

Prosecutors say there’s no evidence Marquez was aware of the attack, however he was accused of purchasing the two guns used in the deadly shooting rampage.