GREEN BAY, Wis. (AP) — Wisconsin transportation officials are trying figure out why a concrete support pier for a highway bridge unexpectedly sank about 2 feet, causing a deep dip in the pavement and leading authorities to shutter the span.

The Leo Frigo Memorial Bridge was closed about 5 a.m. last Wednesday after a long, deep dip was discovered in the pavement. The shutdown snarled traffic in Green Bay, where the bridge carries about 40,000 cars a day over the Fox River on Interstate 43.

Conditions quickly eased, however, as drivers were directed to other routes. Randy Asman, a Wisconsin Department of Transportation traffic engineer, said drivers were rerouted around the city or to the city’s Main Street bridge and the morning commute went smoothly along those detours. Still, he said, drivers should give themselves a little extra time.

Jerry Baranczyk, of Pulaski, said he left 10 to 15 minutes early to get to his job with Procter & Gamble, but he was glad he hadn’t done that on Wednesday.

"I was just lucky I didn’t leave too early," Jerry Baranczyk told WLUK-TV. "I would have been going across it about the time they shut down."

Lori Wescott, of Green Bay, said her morning commute took an additional five to 10 minutes with the detour. On Wednesday, she was just about to get onto the bridge when a police officer pulled her over and told her to take another way to work.

"After knowing what happened, I got really scared," she told the television station.

The bridge closure is not expected to affect most fans coming to Sunday’s Green Bay Packers football game because most take other roads to Lambeau Field, DOT spokesman Kim Rudat said. But, he added, "Anyone who’s been in Green Bay on Packer day knows it’s slow going, and they’ve got to plan their route."

Rudat said the sag in the pavement appears to have developed over a few hours. State and federal investigators are still looking into what caused it.

The pier settled unevenly, with one side dipping 22 inches and the other settling about 27 inches. The dip in the pavement stretches across the width of the bridge, but does not appear to have affected other areas, said Bill Dreher, a DOT engineer and structures design chief. Engineers have been measuring the pier and those close to it every few hours with a laser to make sure there’s no more movement.

"We want to make sure it’s stable first, and then we’ll decide what we can to do get in there and check it out," Dreher said.

The bridge, which opened in 1981, was last inspected in 2012, Rudat said. It’s named for Leo Frigo, a former cheese company president who founded a food pantry for the poor in Green Bay.

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