Sao Paulo suffered a shock 1-0 defeat Wednesday to Bolivian underdogs The Strongest on a night of mixed fortunes for Brazil in South America's most prestigious club competition the Copa Libertadores.

A well-worked 62nd minute strike by Uruguayan Matias Alonso settled a fractious encounter at Sao Paulo's Pacaembu Stadium as the Bolivian minnows clinched their first away win in the Libertadores since 1982.

The victory represented a huge upset for The Strongest against the Brazilians, who hail from the wealthiest domestic club competition in South America.

There was more disappointment for another Brazilian club, Gremio, as they traveled to Mexico to take on Toluca in Group 6.

Two second-half goals from Enrique Triverio secured all three points for the Mexicans as Gremio, winners of the competition in 1983 and 1995, struggled to get to grips with the thin air in a game played roughly 2,700 (8,800 feet) above sea level.

With Sao Paulo and Gremio both slumping to defeats, it was left to Atletico Mineiro and Corinthians to uphold Brazilian honor.

Atletico Mineiro faced a tricky trip across the Andes to take on Peruvian minnows Melgar in Arequipa.

Another upset appeared to be on the cards for the home side when Omar Fernandez bundled the ball home from close range in the 12th minute to put Melgar 1-0 up.

But Atletico fought back with goals from Rafael Carioca and Patric before half-time as the Brazilian side held on to claim a 2-1 victory.

Corinthians were also made to work hard for their 1-0 victory away to Chilean side Cobresal in the mining city of Atacama.

The Group 8 match had seemed destined for a goalless draw heading into injury time until Cobresal midfielder Miguel Escalona put through his own net to hand the Brazilian visitors a narrow victory.