SANTA CLARA — A day after U2 mesmerized sold-out audiences at Levi’s Stadium, Santa Clara leaders threatened to fine the San Francisco 49ers’ venue management for letting the rock band play past the city’s 10 p.m. event curfew — the latest in a series of disputes with the NFL team.

“What happened last night was sad and inappropriate,” said Vice Mayor Dominic Caserta, adding that he’s gotten eight emails from neighbors complaining about the noise.The City Council in January denied a request to extend the curfew for the U2 concert from the San Francisco 49ers, which operates the stadium and has a contentious relationship with Mayor Lisa Gillmor. The team and city leaders have squabbled over stadium finances and access to a nearby soccer park.

On Thursday, Gillmor said Santa Clara will fine the stadium management for blowing the curfew on Wednesday, which she added wasn’t the first time. A Beyonce concert also dragged past 10 p.m., the mayor said, so she’s considering increasing penalties and reviewing the stadium’s contract for potential breaches.

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VTA estimates 6,500 used light rail after U2 concert U2 took the stage at 9 p.m. and played for about two hours, raising a question about whether there was ever any intention of abiding by the curfew.

“We have to protect our neighbors,” Gillmor said. “We’re going to take any legal actions and looking at putting teeth into our enforcement policy.”

The 49ers had no comment on the mayor’s penalty threats.

Caserta, who was on the losing end of the 4-3 vote on the curfew in January, is worried it will discourage major acts from coming to Levi’s Stadium.

“We need to be competitive in the market share and these amazing bands like U2 will look elsewhere and that will hurt our economic vitality long term,” Caserta said. But he added that stadium management still must follow city law.

“Even though I think having U2 in our city is amazing and I’m supportive of the stadium, the council made a decision — the curfew is 10 p.m.,” Caserta said. “I’m very disappointed that neighbors had to hear noise after 10 p.m. and the concert did not follow the will of the council.”

Arnold Aldor, 45, lives across from Levi’s Stadium and said he’s considering leaving the area because of the noise and traffic. He bought his home on Lafayette Street in 2004 — nearly a decade before the stadium opened.

“I have three kids that go to school tomorrow and all three are still up because of the noise,” he wrote in an email to the City Council. “I hate all the extra traffic and noise that the stadium brings. Please do something to prevent any future concerts from going past 10 p.m., especially on a school night.”

The concert by one of rock’s biggest acts was largely a success — earning raves from critics and most fans.

But there were problems early on with fans complaining of being stuck in traffic trying to get to the stadium and park, and finding long lines for food once inside.

“The traffic and parking was outrageous,” said Ronna Kelly, a Piedmont resident who says it took her two hours to get from the freeway exit to the stadium parking lot. Kelly, who paid nearly $200 for a pair of tickets, said she missed the opening act, Mumford and Sons.

Levi’s Stadium officials were sympathetic to patrons but cited logistic realities for many grievances. They said some complaints, like about overtaxed concessions vendors, were a byproduct of the event being a concert, where patrons want to eat first and stay put once the music begins.

Bob Lange, vice president of communications for the 49ers, said an internationally popular act like U2 draws people from out of the area unfamiliar with local roadways. He added that the stadium management, through social media and concert promoter Live Nation, worked to spread the word about getting to the stadium early to account for those likelihoods.

“They don’t know the traffic patterns, and are finding it out for the first time,” Lange said. “These are different crowds that don’t know Bay Area traffic.”

Jim Mercurio, vice president of stadium operations and the venue’s general manager, said most fans were seated for the opening act.

“There were 30,000 people in the gates for Mumford and Sons, which is well beyond what would be typical for a starting act,” Mercurio said.

Lange and Mercurio also said that the stadium did not receive a single complaint on its phone and email hotlines Wednesday night.

Lange said that while the Santa Clara City Council denied the U2 concert curfew extension, it allowed the neighboring Great America amusement park to stay open to 1 a.m. for multiple nights. But Gillmor said that’s “comparing apples and prunes” because roller coasters don’t carry the same noise and traffic impacts as a giant stadium.

Roger Noll, a Stanford sports economist, said Levi’s Stadium has an “unusually difficult” parking and traffic situation, and that requiring a 10 p.m. curfew is highly unusual.

“The notion of having a rock band wind things up at 9:45 p.m. strikes me as dreaming,” Noll said. “But normally, you don’t plop down a stadium in a residential neighborhood. You think about AT&T Park, which is in the middle of downtown San Francisco, and Oakland Coliseum, which is in the middle of nowhere.”

While Noll said he doesn’t expect the 49ers to be “skilled at handling concerts,” the fallout from the complaints can linger.

“This will have a negative effect on future concerts they manage because people had a bad experience,” he said. “The financing of the stadium hinges on non-NFL events being frequent and profitable. They have to engage in serious PR to overcome this.”