Orlando shooter's employer ran two background checks on him, it said, and found nothing

G4S, the company that employed the man believed to have killed 50 people at a nightclub in Orlando, ran two background checks on him, it said, but found "no adverse findings."

And although Omar Mateen, 29, who allegedly went on a hate-fueled shooting spree early Sunday, was interviewed twice by the FBI, there were "no findings reported to G4S," the company said in a statement.

Mateen worked for the U.K.-based company, one of the largest security firms in the world, for nearly nine years. At the time of the shooting, he was off duty, the company said, but had worked at a residential community in South Florida. He also worked for a time as a guard at a facility for juvenile delinquents, his ex-wife said.

In a statement Sunday, John Kenning, G4S's regional chief executive for North America, confirmed that Mateen had worked for the company since September 10, 2007. It was not clear whether Mateen was required to carry a firearm in his duties for the firm.

"We are shocked and saddened by the tragic event that occurred at the Orlando nightclub," Kenning said. "We are cooperating fully with all law enforcement authorities, including the FBI, as they conduct their investigation. Our thoughts and prayers are with all of the friends, families and people affected by this unspeakable tragedy."

The firm said that he "was subject to detailed company screening" when he was recruited in 2007 and again in 2013. A spokesman for G4S said that the background checks it performed on Mateen involved a personality test, and that the firm checked his employment history and his driving record, performed a drug test and looked at his credit history. He said that the company seeks to re-screen 15 percent of its workforce every year.

The FBI investigated him twice over concerns about possible connections to terrorism. The probes turned up nothing, and Mateen was able to legally purchase firearms days before the shootings.

G4S is one of the world's largest security firms, with a workforce rivaling the population of Washington, D.C., that has worked with U.S. agents on border patrol, provided security to the London Olympics and responded to the recent wildfires in Canada.

The company is based south of London and has 623,000 employees in 110 countries. It has a long history of serving as a U.S. government contractor, working with many agencies, including the Departments of Homeland Security, State and Labor, and the Army. Although most of its revenue comes from the United Kingdom and Ireland, about 20 percent comes from the United States, according to its website.

The company has received about $370 million for work in Florida since 2010, according to a review of federal contract databases. In that time frame, it received more than $831 million nationwide, much of it from the Department of Homeland Security.

G4S also held a contract reportedly worth $355 million to provide security for the 2012 London Olympics. But less than a month before the opening ceremony, it said it was not able to provide the number of guards required. At the time, chief executive Nick Buckles reportedly said, "Clearly we regret signing it but now we have to get on and deliver it." He also agreed that it was a "humiliating shambles" for the company.

In the United States, G4S provides support to federal and local law enforcement. It has contracts with the Department of Homeland Security to provide border protection and works with Immigration and Customs Enforcement to transport illegal immigrants. It says its employees have backgrounds in the military or law enforcement or hold degrees in the criminal justice field.

G4S also does extensive work with the oil and gas and retail industries and provides security at ports and airports.

The company says on its website that it "requires applicants to go through psychological, background and criminal screening. Every G4S security officer participates in a training program that far exceeds industry standards, becoming a specialist trained to both recognize and react to unique hazards of an assigned post."

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Steven Rich, Julie Tate and Alice Crites contributed to this report.