While Sørum competed at last month’s FIVB four-star tournament in Qatari capital Doha with Svein Solhaug, Mol has been sidelined with a hip injury.

The three-European champions last featured together on the international stage at the 2019 FIVB World Tour Finals in Rome in Italy where they claimed bronze.

And Mol and Sørum picked up from where they left off as they defeated Miguel Sarabia and Raymond Stephens of Mexico 21-11, 21-10 in Pool A in the first of three four-star events being held in Cancun to allow players the chance to fulfill qualification criteria for the Olympics.

"It's been a while and it's so good to be back on the World Tour with Anders, it's really amazing," said Sørum.

"The way we won the first match was also amazing.

"The young Mexican team had good serves and good ball control, but we played a really good match and I’m happy about that."

Reigning world champions Oleg Stoyanovskiy and Viacheslav Krasilnikov also won their first match as the Russians saw off Italian qualifiers Jakob Windisch and Samuele Cottafava 21-13, 21-10 in Pool C.

Stoyanovskiy and Krasilnikov will now meet Brazilians Andre Loyola and George Wanderley, who defeated Canadians Ben Saxton and Grant O’Gorman 21-14, 21-18.

The first major upset in the men’s main draw was caused by 31st seeds Theo Brunner and Chaim Schalk of the United States.

The Americans came from behind to beat Brazilian second seeds Alison Cerutti and Alvaro Filho 17-21, 21-18, 15-13.

They will next play for top spot in Pool B against Italians Daniele Lupo and Paolo Nicolai while Cerutti and Filho will compete with Germans Julius Thole and Yannick Harms for third place.

Fourth seeds Jake Gibb and Taylor Crabb of the US and fifth-seeded Nils Ehlers and Lars Fluggen of Germany were also surprised by teams coming from the qualifiers.

The Americans lost 25-23, 21-19 to Swiss pair Quentin Metral and Yves Haussener, while the Germans fell to Brazilians Arthur Mariano and Gustavo Carvalhaes 14-21, 21-15, 17-15.

In the women’s main draw, Cuban qualifiers Leila Martínez and Maylen Deliz won both of their group matches to advance to the last 16.

The Cubans overcame Australians Taliqua Clancy and Mariafe Artacho del Solar, ranked fifth in the world, with a 21-17, 13-21, 15-11 triumph before beating 2018 European champions Sanne Keizer and Madelein Meppelink of The Netherlands 21-19, 21-12.

"It was an incredible day for us," said Deliz.

"To win matches against teams at this level is so important.

"We haven’t played on the World Tour in the last two years, but we’ve been training and preparing for this moment and it’s important to see that our hard work is showing now."

Other teams to win their pools were Brazilians Agatha Bednarczuk and Eduarda Lisboa and Talita Antunes and Taiana Lima, Americans April Ross and Alix Klineman, Canada's Sarah Pavan and Melissa Humana-Paredes, Germans Laura Ludwig and Margareta Kozuch, Switzerland's Nina Betschart and Tanja Huberli and Russia's Nadezda Makroguzova and Svetlana Kholomina.

Three of the eight pools were decided in three-setters with Ross and Klineman defeating Canadians Heather Bansley and Brandie Wilkerson 21-16, 18-21, 15-13 in Pool A, Pavan and Humana-Paredes downing Germany's Chantal Laboureur and Cinja Tillmann 21-19, 22-24, 15-8 and Ludwig and Kozuch prevailing 21-19, 17-21, 15-10 in an all-German clash with Sandra Ittlinger and Kim Behrens.

Competition is due to continue tomorrow.