The 15th seeds posted a 21-9, 21-16 victory over 19th-seeded Alvaro Filho and Vitor Felipe of Brazil in the opening elimination round before defeating 26th-seeded qualifiers Martins Plavins and Haralds Regza of Latvia 21-18, 21-19 to reach the quarter-finals. 

The reigning Pan American champions thus moved into the top 15 pairs on the Rio 2016 provisional ranking list, increasing their qualifying total to 4,670 points for their best 12 finishes at FIVB World Tour stops or continental championships since the start of the process.

Mexico’s volleyball team secured its Rio 2016 berth earlier this month at the men’s World Olympic Qualification Tournament in Mexico City.

"It has been a long and stressful journey," said the 32-year old Ontiveros.

"To join our indoor team in Rio is significant for the development of volleyball and beach volleyball in our country.

"I am so thankful right now.

"It is hard to describe my emotions right now.

"Despite the stress of the last month, it has been a wonderful experience to finally reach the ultimate goal in playing in the Olympics for Mexico."

Virgen and Ontiveros now face top-seeded Alison Cerutti and Bruno Oscar Schmidt of Brazil in tomorrow’s quarter-finals.

Like the Mexicans, Germany's Markus Bockermann and Lars Fluggen had to win twice today to reach the last eight and they moved half way towards achieving that feat by overcoming compatriots Jonathan Erdmann and Kay Matysik 21-17, 21-18.

Victory ensured them a Rio 2016 berth and full of confidence, they went on to defeat 18th-seeded Grzegorz Fijalek and Mariusz Prudel of Poland 21-19, 21-18.

Awaiting the 16th seeds in the quarter-finals are 12th-seeded Konstantin Semenov and Viacheslav Krasilnikov of Russia, who beat Latvia’s Aleksandrs Samoilovs and Janis Smedins 21-19, 21-12 in the second elimination round.

In the women’s draw, the United States' April Ross and Kerri Walsh-Jennings booked their place in the semi-finals with a 21-17, 21-14 win over 16th-seeded Elsa Baquerizo and Liliana Fernández of Spain.

The Americans earlier defeated 15th-seeded Jamie Broder and Kristina Valjas of Canada 21-17, 12-21, 15-5 and fifth-seeded Heather Bansley and Sarah Pavan, also of Canada, 21-17, 21-19.

They next go on to meet Germany's Laura Ludwig and Kira Walkenhorst, who after eliminating Canada’s Melissa Humana-Paredes and Taylor Pischke with a 21-18, 21-16 win, advanced to the semi-finals with 21-13, 22-20 victory over sixth-seeded Juliana Felisberta and Taiana Lima of Brazil.

Brazil’s Agatha Bednarczuk and Barbara Seixas ousted Italy’s Marta Menegatti and Viktoria Orsi Toth in their first match of the day before eliminating ninth-seeded Louise Bawden and Taliqua Clancy of Australia 21-23, 26-24, 15-8 in the last eight.

Awaiting them in the semi-final are compatriots Talita Antunes and Larissa Franca, who posted a 21-18, 21-12 quarter-final win over eighth-seeded Madelein Meppelink and Marleen van Iersel of The Netherlands after seeing off Vanuatu’s Linline Matauatu and Miller Pata. 

The remaining pairs make up the top four of the Rio 2016 provisional ranking list with Antunes and Franca leading the way on 7,620 points.

Bednarczuk and Seixas are second on 7,070 points, while Ross and Walsh-Jennings are third on 6,670 and Ludwig and Walkenhorst fourth on 6,260.