Monterrey Security, the company that provides various security services at the US Bank Stadium in Minneapolis, Minnesota, is to face a state-led investigation over its hiring practices.

According to KSTP-TV, sources close to the matter have said the probe involves falsification of government documents, failure to conduct proper background checks and hiring people with a criminal record without full clearance.

KSTP-TV added that the investigation involves hundreds of staff at the firm.

The Star Tribune newspaper reports that Monterrey is in the first year of three-year contract with the US Bank Stadium, which only opened in July last year. The venue is home to NFL American football franchise the Minnesota Vikings.

Ongoing investigation

The company came under fire during a Vikings game earlier this year when two protestors were able to drop down from scaffolding at the stadium to unfurl a banner with a slogan opposing a pipeline.

In a statement, SMG, operator of the US Bank Stadium, said: “We expect that Monterrey Security will cooperate fully with state officials for the ongoing investigation.

“Upon the completion of this investigation, SMG will take appropriate action. … The safety and security of all guests and employees of US Bank Stadium continues to be our top priority.”

The Minnesota Sports Facilities Authority is not due to meet again until June 22, but chairwoman Kathleen Blatz said she does not expect any action to be taken against Monterrey.

Blatz added: “I would assume they know what they’re doing; I can’t believe it’s just wholesale neglect of the rules.”