About 13 hours before the match was set to begin, Pinnacle’s traders suspended betting on it, Blume said. He then notified the police in Victoria, the Australian state where the tournament takes place, of possible irregularities.

“The law enforcement agencies are watching this area very closely,” said John Eren, the minister of sport for Victoria. “Of course we’ve seen it in many different sports, not just tennis. And that’s really sad because at the end of the day, 99.9 percent of the sport-loving community don’t behave in that way. It’s important to stamp these out very quickly, and I’m hoping that the relevant authorities will act quickly and swiftly to deal with some of these matters.”

The police said they worked with Australian tennis officials throughout the tournament but would not confirm whether they had been alerted to the irregularities or were investigating this particular match.

Blume said of Pinnacle, “We saw a small number of people placing a large amount of money.” He added: “In context, these matches are rather small. That means that any aggressive betting behavior is very easy to detect on our side.”

Blume said Pinnacle had seen no such betting behavior for any other match at this Australian Open.

First-round mixed doubles matches typically generate little gambling action, but more than $25,000 had been wagered on another website, the betting exchange Betfair, a few hours before the match was scheduled to start. By comparison, three other mixed doubles matches scheduled for similar times on Sunday had generated less than $2,000 combined.

“We have a specialist team who monitor our markets and work closely with sports governing bodies, including the T.I.U., to investigate any suspicious betting patterns that arise,” said James Midmer, a spokesman for Betfair. “Due to the nature of this team’s work, we can’t comment on speculation surrounding individual sports and events.”

Stefano Berlincioni, a sports gambling expert from Italy who writes for the website Last Word on Sports, last year highlighted a doubles match involving Marrero that Berlincioni believed was suspicious. He said Sunday that his analysis of the wagering activity around the Australian Open match indicated it might have been fixed.