Authorities in California on Thursday arrested three people tied to one of the San Bernardino attackers on charges of marriage fraud, conspiracy and lying under oath.

None of these charges directly relates to the terrorist attack last year, but the FBI says these counts stemmed from the investigation into the Dec. 2 shooting carried out by Syed Rizwan Farook and his wife.

Prosecutors said that Farook’s brother — Syed Raheel Farook — was arrested after being charged with a marriage fraud conspiracy. Raheel’s wife, Tatiana Farook, and her sister, Mariya Chernykh, were also arrested, the U.S. Attorney’s Office for the Central District of California said Thursday morning.

According to an indictment returned Wednesday by a federal grand jury and unsealed Thursday, all three have been accused of lying under oath to gain immigration benefits for Chernykh, 26.

Federal agents investigating the shooting have now arrested four people with connections to the two attackers, who killed 14 people in a rampage believed to have been inspired by the Islamic State.

Chernykh, 26, is married to Enrique Marquez Jr., who bought the assault rifles used in the San Bernardino attack and was charged in December with conspiring to carry out other attacks with Farook in 2012. These other plans were never carried out, but prosecutors say they became very detailed, with participants discussing strategies for assaulting a heavily-trafficked road in Riverside, Calif., so that they could kill motorists and first responders alike.

In addition to the charges for these earlier plots, Marquez was also accused of defrauding immigration services by entering into a sham marriage with Chernykh.

Marquez was a close friend of Farook and, federal authorities say, bought the two assault-style guns that Farook and his wife, Tashfeen Malik, used in the shooting. The indictment unsealed Thursday said that Marquez married Chernyhk to obtain immigration benefits for her.

Prosecutors alleged that in applying for benefits, they falsely stated they lived at an address in Corona, which was also Raheel and Tatiana Farook’s address. Authorities also said that when they were investigating the shooting and interviewed Chernykh, she told them she lived with Marquez at the home in Coronado.

In February, the FBI said that it had served a search warrant at a home in Corona. No arrests were made, and the affidavit for the warrant was sealed by a court, according to the FBI, but local media reports said they were at the home belonging to Raheel and Tatiana Farook. On Thursday morning, the FBI executed warrants in Corona and Ontario, where authorities say Chernykh lives, to arrest the three of them.

The grand jury charged Chernykh, 26, and her sister and brother-in-law — both 31 — with lying under oath on immigration paperwork, which carries up to five years in prison. Chernykh was also charged with fraud, perjury and lying to federal agents, all of which could bring a sentence of up to 25 years in prison.

“Today’s arrests open a new phase in the process of bringing to justice all individuals who allegedly committed crimes that were uncovered during our exhaustive investigation,” U.S. Attorney Eileen M. Decker said in a statement. “The charges also reflect the importance we place on statements made to law enforcement officials during a terrorism investigation. Those who lie to or conceal material information from law enforcement officers investigating terrorist acts will be prosecuted to the fullest extent of the law.”

The shooting in San Bernardino “showed yet again how our nation’s legal immigration system can be subverted and exploited by those intent on doing this country harm,” Joseph Macias, special agent in charge of the U.S. Immigration and Customs Enforcement’s Homeland Security Investigations arm in Los Angeles, said in a statement.

In November 2014, Chernykh and Marquez opened a joint banking account and listed an address in Riverside as their residence, according to the grand jury indictment. Later that month, they stated on a Riverside County marriage certificate that they were wed at a religious institution in Corona. They posed for pictures, prosecutors said, to “create the false impression” that they had a legitimate marriage.

In July 2015, Marquez petitioned for a green card for Chernykh to give her legal resident status. He used the Forum Way address in Corona. In an instant message exchange last November, Marquez and Chernykh discussed their mutual anxiety for their upcoming immigration interview “due to the lack of contact with each other,” the indictment states.

That month, Marquez also allegedly told Chernykh that he was worried about being jailed for fraud after the interview. He stated on social media that he was involved in terrorist plots and might go to prison for fraud, according to the indictment.

On Nov. 30, in an instant message exchange, Chernykh told Tatiana Farook that she planned to meet Marquez at the Forum Way address to prepare for their immigration interview. On Dec. 1, Raheel Farook created a lease agreement dating back to Nov. 1, 2014 to make it appear that Marquez and Chernykh had resided together at that address, the indictment alleged. That same day, Tatiana Farook accompanied Chernykh to buy a $50 wedding ring for Marquez from a jewelry store in Riverside.

No attorneys were immediately listed for the three people arrested Thursday. They were all scheduled to be arraigned at a federal court in Riverside later in the day. Before the arrests, federal prosecutors had asked for the three people to be detained before trial.

This story has been updated multiple times with new information. First published: 12:36 p.m.

Further reading:

No links to foreign terrorists found on San Bernardino iPhone

‘Where’s Syed?’ How the San Bernardino shooting unfolded