JUPITER, Fla. — Robert Kraft, the billionaire owner of the New England Patriots, faces charges of soliciting a prostitute after he was twice videotaped in a sex act at a shopping-centre massage parlour in Florida, police said Friday.

The 77-year-old Kraft denied any wrongdoing. The case comes amid a crackdown on sex trafficking from Palm Beach to Orlando in which police planted cameras in massage parlours.

Kraft was not immediately arrested. Jupiter police said a warrant will be issued and his attorneys will be notified. They said details about the misdemeanour charges against the owner of the Super Bowl champion team will not be released until next week.

Hundreds of arrest warrants have been issued in recent days as a result of the six-month investigation, and more are expected. Ten spas have been closed, and several people have been taken into custody on sex trafficking charges.

Jupiter Police Chief Daniel Kerr said he was shocked to learn that Kraft, who is worth $6 billion, was paying for sex inside a shopping-centre massage parlour, the Orchids of Asia Day Spa. "We are as equally stunned as everyone else," Kerr said.

Most people charged for the first time with soliciting a prostitute in Florida are allowed to enter a diversion program, said attorney David Weinstein, a former prosecutor. Kraft would probably have to perform 100 hours of community service and attend a course on the harmful effects of prostitution and sex trafficking, he said.

The arrest could also get Kraft in trouble with the NFL, which in a statement said only that it is "aware of the ongoing law enforcement matter and will continue to monitor developments."

Under league policy, players, owners, coaches and other employees can be punished for "conduct detrimental to the integrity of and public confidence in" the NFL.

"Ownership and club or league management have traditionally been held to a higher standard and will be subject to more significant discipline," the policy says.

The Patriots won the Super Bowl this month over the Los Angeles Rams for their sixth NFL championship in the past 18 seasons, making them the most successful team in pro sports during that span. Before the Super Bowl, several retired NFL players appeared in a public service announcement decrying sexual exploitation and human trafficking in Atlanta, the host city.

Kraft lives in Massachusetts and has a home in the Palm Beach area. Though he is a Democrat, he is friendly with President Donald Trump and a frequent guest at Trump's Mar-a-Lago club. Kraft's wife, Myra Hiatt Kraft, died in 2011. He has been dating 39-year-old actress Ricki Noel Lander since 2012.

"Well it's very sad. I was very surprised to see it. He's proclaimed his innocence, totally," Trump said at the White House on Friday.

In a statement, Kraft's representatives said they "categorically deny that Mr. Kraft engaged in any illegal activity."

The spa Kraft allegedly visited is in a busy, upper-middle-class shopping centre with neighbours that include a dentist, a real estate office, surf and bike shops and a Publix supermarket.

After hearing about the arrest, Brian Rubino, a Patriot fan who lives nearby, went by the spa wearing a team jersey. He said Kraft made a mistake, but he could see how it might happen.

"A 77-year-old man, lost his wife, who knows? I see how you can end up in a place like this," Rubino said.

Vero Beach police Chief David Currey, whose agency has been involved in the sex-trafficking investigation, told reporters earlier this week that the prostitutes are victims who have been trapped into the trade.

"These girls are there all day long, into the evening. They can't leave and they are performing sex acts," Currey said, according to TCPalm. "Some of them may tell us they're OK, but they're not."

The owner of Orchids of Asia Day Spa, 58-year-old Hua Zhang, was arrested Tuesday on 29 prostitution and related charges. Police in her arrest report said they watched video of her employees performing various sex acts with two dozen customers. Her attorney, Gennaro Cariglio Jr., had no comment.

Kraft, who made his initial fortune through a packaging company, bought the Patriots in 1994 for $172 million to keep the team from moving to St. Louis. He hired Bill Belichick as coach in 2000, and the team later drafted quarterback Tom Brady, launching its nearly two decades of success.

In 2007, the Patriots got in trouble for filming other teams' signals. The NFL fined the team $250,000 and Belichick $500,000. In 2014, Brady was accused of deflating game footballs to gain a better grip. He served a four-game suspension, and the Patriots were fined $1 million.

Kraft was not implicated in either scandal.