Two protesters climbed a massive roof truss inside U.S. Bank Stadium on Sunday afternoon and then, as thousands of astonished Vikings fans watched, dropped down to unfurl a banner protesting the Dakota Access oil pipeline.

Minneapolis police officers and firefighters quickly made their way to the spot and spoke to the protesters from a catwalk above them, but left the pair dangling and their banner undisturbed until the game was over and the stadium began emptying out.

Karl Mayo, 32, and Sen Holiday, 26, were booked into the Hennepin County jail on charges of burglary and trespassing, both gross misdemeanors. Carolyn Feldman, 27, also was booked on a related misdemeanor charge, obstructing the legal process, according to the Minneapolis Police.

The high-wire protest began about 12:47 p.m., early in the second quarter of the Vikings-Bears football game, when the two men managed to clamber over a guardrail from a public concourse, then climb up a built-in ladder to a catwalk high above the purple seats.

From there the men appeared to attach their banner to the ridge truss, then dropped down themselves using ropes and harnesses around their waists and legs.

The rectangular white banner bore the USBank logo and the words, "Divest #NoDAPL," a reference to the Dakota Access Pipeline in North Dakota, which has been the subject of national controversy and a monthslong protest encampment.

On the field, the final game of the team's snakebit inaugural season in the new stadium went on without interruption and the Vikings won.

While the men dangled on high, security guards cleared fans from eight rows of seats in Section 120 just below. The truss the men climbed is just to the north of the giant video screen in the stadium's east end zone.

Mayo, who wore a purple Brett Favre No. 4 Vikings jersey, occasionally waved and smiled at the fans below and appeared to converse with law enforcement officers who were about 40 feet above on the catwalk.

Initially, a Minneapolis Police officer climbed up to the catwalk, then came back down. Police later said he was a crisis manager. More firefighters and police climbed the ladder to the catwalk and remained there for the second half.

The two men remained aloft until the game's conclusion, when they hoisted themselves with apparent ease back up and onto the catwalk as the stadium's sound system blared the Counting Crows song "Hanging Around."

The lingering postgame crowd cheered when the protesters climbed onto the catwalk, but booed them when they were safely back down the ladder. The banner remained in place as fans left.

Rueful quarterback

At his postgame news conference, Vikings coach Mike Zimmer said, "I swear to God I didn't see them."

Quarterback Sam Bradford, when asked about the protesters, said ruefully, "Why wouldn't the season end like that?"

The two climbers were arrested, then evaluated by a physician from nearby Hennepin County Medical Center. Neither was injured and both refused medical treatment, the police said.

While the men hung above the crowd, protest organizers e-mailed a release to news outlets quoting Holiday saying, "We are here in solidarity with water protectors from Standing Rock to urge U.S. Bank to divest from the Dakota Access Pipeline."

The protest's organizers contend that U.S. Bank has tens of millions of dollars in credit lines active with the pipeline's parent company.

While no one was hurt in the protest, the climbing was risky. There is no supportive netting or cage under or around the ladder used to reach the catwalk on the truss, and the climbers risked a long fall. The stadium's highest point is the 270-foot prow, which is on the western end of the building opposite the side the climbers used.

Police said Sunday afternoon that they will meet with all stadium partners to investigate the incident and how the young men gained access to the stadium's ceiling structure.

NFL games are high-security events, and it's unclear how the two protesters got in. All fans must pass through metal detectors to enter the building. Purses must be within strict size limits and/or be clear plastic. Everyone who enters the building is subject to a search at the entrance.

Construction of the pipeline has been on hold for several weeks, the result of a yearlong battle between the petroleum industry and a coalition of American Indian tribes and environmentalists. The tribes and their supporters won a round last month, when federal officials put a hold on a final stretch of construction, but the expectation is President-elect Donald Trump will push the pipeline to completion.

Star Tribune staff writer Paul Walsh contributed to this report.