Robinho scored a hat-trick to give Brazil a badly-needed 3-0 Copa America win over Chile on Sunday, while Mexico reached the quarter-finals after beating Ecuador 2-1.
Mexico's win, which started with another goal by striker Nery Castillo, made them the first team to reach the final eight of the tournament.
They lead Group B with six points, followed by Brazil and Chile on three. Ecuador are virtually out of the running after two defeats.
The 52,000-capacity Monumental stadium in Maturin, Venezuela, built from scratch in less than a year, was ruled fit to stage the games even though it was clearly not ready.
The area around the arena was a sea of mud strewn with building materials and piles of debris. Inside, dust covered the seats and more debris was piled into corners of the stadium.
The competition's ticketing crisis continued, leading to queues of several hundred metres built up under a baking tropical sun.
Many fans who had booked tickets online and by telephone had not received them, even though their credit cards had been debited.
The fans inside the ground were treated to Robinho at his best although Brazil needed a controversial penalty to get off the mark in the 36th minute.
Paraguayan referee Carlos Torres apparently gave the kick for pushing and Robinho calmly scored with a low shot amid Chilean protests.
CHILE UNIMPRESSED
Chile squandered several chances to equalise after halftime before Robinho added two more in the last 10 minutes.
He latched on to Vagner Love's pass to chip the ball over Claudio Bravo in the 84th minute and was on target again after a dazzling 40-metre run three minutes later.
Chile coach Nelson Acosta, whose team have conceded 12 goals and scored none in their last three meetings with Brazil, was unimpressed.
"He scored at the end of the match when our defence was completely open," said Acosta.
"It's very easy to score when your opponents are tired and chasing the game."
In the second match of the double bill, Castillo -- scorer of a superb effort against Brazil -- took advantage of hesitation in the Ecuador defence to slot the ball home after a Rafael Marquez pass in the 22nd minute.
Two Mexican substitutes combined to produce the second in the 80th minute when striker Cuauhtemoc Blanco floated over a superb cross from the right wing and Omar Bravo bulleted home a diving header.
Blanco's participation was the perfect answer to media reports that he had considered quitting the team because he was not being picked.
The player known as the Camel because of his hunched-back style had angrily denied the reports.
Ecuador looked demoralised but they gave themselves a glimmer of a chance with a deflected strike from more than 20 metres out by Edison Mendez.
"Yes, it's a failure and I'm not thinking of resigning for the moment," said Ecuador coach Luis Fernando Suarez.
