U.S. Bank Stadium contractor Mortenson Construction and subcontractor Berwald Roofing face fines of $173,400 for "serious" and "willful" safety violations in the death of one worker and injury to another last August.

The two companies were cited after an investigation by the state Department of Labor's Occupational Safety and Health Administration (OSHA). The inspection reports, with citations and fines, were posted on the federal Department of Labor's website.

The reports don't provide an explanation of the accidents, but the largest fine — $70,000 — and most serious alleged violation faults Berwald for willfully failing to have workers use proper fall protection while working at heights above 6 feet.

To issue a citation for a "willful" violation, an investigator must determine an employer was aware of a hazardous condition and made no reasonable effort to eliminate it. Willful violations are uncommon.

It's never been publicly stated whether the workers, who were Berwald employees, were wearing safety harnesses. This latest citation is the closest official indication that something wasn't properly in place.

Early on a workday last August, Jeramie Gruber, 35, a Faribault native, died and a second worker, who has not been identified, was seriously injured in a fall from the massive building. The injured man suffered a gash on his leg that required 48 stitches.

A previous OSHA report described the incident: "While installing a solid roof, two roofers fell and slid down the roof. One struck a post and stopped, but was injured. The other broke through a guardrail and fell onto an elevated platform below."

Gruber was the only man to die on the construction project, which started in early 2014 with the demolition of the Metrodome on the same site. The building is on the verge of opening for public tours in late July and for the first sporting event on Aug. 3. The $1.1 billion stadium is the most expensive public-private project in state history and will be the new home of the Minnesota Vikings beginning this year.

Mortenson Senior Vice President John Wood said in a statement that the company is still working with OSHA regarding a "final determination relative to its citation."

Eugene Berwald, president of the roofing company, issued a similar statement, saying his company is "continuing to cooperate" with the state OSHA.

An OSHA spokesman declined to comment on the open case.

The closed-door negotiating process can take months or years depending on how much the contractors dispute findings and fines.

In the filings obtained Wednesday, Minneapolis-based Mortenson was cited for one "serious" workplace safety violation and faces a $34,300 fine.

The same investigation found one "willful" and two "serious" violations by North St. Paul-based Berwald. The citations imposed $139,100 in fines against the roofer.

In addition to Berwald's citation for failing to use proper fall protection, the citations fell under two other categories.

Mortenson was cited under "general safety," which requires "frequent and regular inspections of the job sites, materials and equipment."

Berwald Roofing also was cited for a general safety violation. The third citation for Berwald was under the general duty clause, requiring employers to provide a workplace free of hazards likely to cause death, injury or harm.

Ultimately, any serious or willful violation that contributes to the death of an employee must result in a minimum $50,000 fine for a willful violation and a $25,000 minimum for a serious violation.

As he has in the past, Wood expressed sadness about the accident. "At Mortenson, safety is a core value, and we are committed to eliminating the risk of injury on all of our projects," he said.

In five years preceding the accident, Berwald, which has a $3.4 million contract on the stadium, received nine worksite citations for serious violations during six inspections and faced fines totaling more than $12,500.

Most of the violations were for workers failing to use safety harnesses and not being protected by guardrails.

According to federal documents, neither Mortenson nor Berwald had any other accidents in at least the past 15 years.

Twitter: @rochelleolson