Story highlights

NEW: Two of three suspects head home; third transferred to immigration hold

They are indicted on charges related to marriage fraud, prosecutors say

There's no indication the three had advance knowledge of terror attacks, sources tell CNN

Riverside, California CNN  — 

Federal authorities have arrested three people in a criminal marriage fraud investigation linked to San Bernardino, California, terrorist Syed Rizwan Farook, the U.S. attorney’s office said Thursday.

Prosecutors said the trio, along with a former friend of Farook’s, engaged in a conspiracy to obtain immigration benefits for a sibling of Farook’s sister-in-law.

A grand jury indicted them Wednesday, prosecutors said.

The three entered not-guilty pleas on Thursday.

Those arrested were identified as Syed Raheel Farook, the brother of one of the San Bernardino shooters, as well as Syed Raheel Farook’s wife, Tatiana Farook, and her sister, Mariya Chernykh.

Raheel Farook and his wife Tatiana leave court after pleading not guilty to marriage Fraud charges.

According to authorities, former Farook friend Enrique Marquez Jr. received money to marry Chernykh to help her obtain immigration benefits.

U.S. Judge David T. Bristow made it clear this was a case of marriage fraud.

“It is not about acts of terrorism,” he said.

Marquez is awaiting trial on charges of conspiring with Syed Rizwan Farook to provide material support to terrorists. He is also awaiting trial on marriage fraud charges.

There is no indication those arrested had previous knowledge of the December attack in which Syed Rizwan Farook and his wife, Tashfeen Malik, killed 14 people, two law enforcement sources told CNN.

The three suspects shuffled into federal court in leg irons.

After working out bail – $25,000 for Syed Raheel Farook, and $35,000 for Tatiana Farook – the two were released.

The pair, who are both 31, will be back before a judge on June 21 in federal court in the Los Angeles area for trial.

Chernykh, 26, was ordered to Immigration and Customs Enforcement detention for immigration violations.

She not only faces the marriage fraud charges but also is suspected of lying to federal agents.

CNN’s Paul Vercammen reported from Riverside, California, and Pamela Brown reported from Washington. CNN’s Michael Pearson reported and wrote from Atlanta. CNN’s Steve Almasy contributed to this report.