TAMPA, Fla. (Reuters) - More than 50 victims and survivors of the June 2016 massacre at a Florida nightclub sued the gunman’s employer and widow on Wednesday, blaming them for failing to prevent the deadliest mass shooting in modern U.S. history.

FILE PHOTO - The Pulse nightclub sign is pictured following the mass shooting last week in Orlando, Florida, U.S. on June 21, 2016. REUTERS/Carlo Allegri/File Photo

The lawsuit filed in the U.S. Southern District of Florida accused the security firm that hired shooter Omar Mateen of ignoring his comments supporting violence prior to the rampage that killed 49 and injured dozens at a gay nightclub in Orlando.

The lawsuit accuses Mateen’s widow, Noor Salman, of conspiring in the attack by assisting with his purchase of firearms and surveillance of the Pulse nightclub. She faces federal charges of aiding and abetting her husband and obstructing justice by lying to authorities.

The civil lawsuit seeks unspecified financial damages on behalf of 57 victims, including survivors and the representatives of several who died. Mateen was killed in a shootout with police after a three-hour standoff inside the club.

G4S Secure Solutions, the Florida-based security firm employing Mateen, failed to adequately assess his psychological state, the lawsuit said, and should have removed his service weapon and recommended his state firearms license be revoked.

“They had the best chance to do something about it and did nothing,” Chicago-based attorney Antonio Romanucci said at a news conference in Orlando.

G4S Secure Solutions said in a statement it planned to “vigorously defend itself against the lawsuit which it considers to be wholly without merit.”

Also named in the lawsuit was its Britain-based parent company, G4S Plc, the world’s largest global security firm.

Several plaintiffs spoke at the news conference about the horror they experienced during the attack and expressed anger that warnings about Mateen were not heeded.

“To not have anyone do anything about it makes no sense to me,” said Ilka Reyes, who was shot multiple times.

Following scrutiny of Mateen’s files after the shooting, Florida state officials fined G4S Secure Solutions for providing inaccurate psychological testing information on forms that allowed employees to carry guns.

At the time, the company said it learned in 2013 that Mateen had been questioned by the FBI but was unaware of a subsequent interview in 2014. Legal experts noted the difficulty of establishing liability against employers.

Salman’s attorney, Charles Swift, had not received the lawsuit on Wednesday. He said in an email Salman has pleaded not guilty and has denied responsibility for her husband’s actions.