The wife of Orlando nightclub gunman Omar Mateen knew her husband was going to attack and had assisted him, prosecutors said on Tuesday, seven months after 49 lives were lost in the deadliest mass shooting in the U.S. history.

"She knew he was going to conduct the attack," assistant US Attorney Roger Handberg told the federal court in Oakland, one day after Noor Salman was arrested at her parents' home in the San Francisco suburb of Rodeo.

She was charged of aiding and abetting her husband, who pledged allegiance to the extreme group Islamic State during the attack on June 12.

Investigators believe Salman acted of her own free will and knowingly took steps to obstruct the probe into the massacre, a CNN report quoted law enforcement officials as saying.

Months before the attack, Mateen added the name of his wife to his life insurance policy and made sure she had access to his bank accounts. He also bought his wife an expensive piece of jewelry, said the report.

Two hours after the attack started, Mateen texted his wife at 4 a.m. and asked her whether she had heard any news about the shooting. At one point, Salman sent a text to Mateen saying that she loved him, a law enforcement official said.

Her family, meanwhile, maintains she had no idea that her husband was going to attack the popular Pulse nightclub.

"Noor Salman had no foreknowledge nor could she predict what Omar Mateen intended to do that tragic night," family attorney Linda Moreno of Tampa, Florida, said Monday.

Her case will be heard in Florida afterwards, where the killings happened and where Salman and Mateen lived with their young son at the time, Handberg said.

"This is a matter that we continue to take very seriously," Attorney General Loretta Lynch said on Monday when confirming Salman's arrest.

"We said from the beginning we were going to look at every aspect of this case, every aspect of this shooter's life - to determine not just why did he take these actions, but who else knew about them, was anyone else involved, is there any other accountability that needs to be had here in this case." said Lynch.

Salman married Mateen in 2011 and lived with him and their son in Fort Pierce, Florida. Authorities interviewed Salman immediately after the shooting, but she remained free until Monday.

source: Xinhua