A men's doubles match at Wimbledon involving the Spanish pairing of Fernando Verdasco and David Marrero is being investigated for match-fixing.

The first-round doubles match – where Verdasco and Marrero lost to João Sousa and Leonardo Mayer 7-6 (8-6), 6-4, 6-7 (7-9), 6-1 – was flagged by anti-corruption investigators due to suspicious betting behaviour.

Online gambling website Pinnacle Sports observed "a series of bets from accounts with a history of wagering on suspicious matches", the New York Times reported. The probe was initially reported by ABC.

The bets were placed an hour before the match began.

"We followed our strict protocol when it comes [to] match-fixing alerts by notifying the authorities on site at Wimbledon and reducing our market offering immediately," Pinnacle manager Sam Gomersall told ABC News.

Marrero said he was surprised that he was under investigation.

"I was at home packing my suitcase because tomorrow, Friday, I'm heading to Germany, and this news caught me by surprise. I had no idea. What do want me to say? Just like always, go ahead and investigate because I'm very much at ease," Marrero told EFE.

This is the second time Marrero has been investigated for purported match-fixing after a similar incident at a 2016 Australian Open mixed doubles match.

Marrero and his then partner Lara Arruabarrena, along with opponents Lukasz Kubot and Andrea Hlavackova were all investigated but subsequently cleared by the Tennis Integrity Unit.

Marrero is ranked No.54 in doubles and has ranked as high as No.5 in doubles in his career.

His partner Verdasco is an accomplished singles player who reached the 2009 Australian Open semifinals, losing to countryman Rafael Nadal, and has a career-high singles ranking of No.7.