Paraguayan outfit Cerro Porteno struck twice in the opening eight minutes in a 2-1 win at home to Chile's O'Higgins.
They are top of the group on seven points, one ahead of Deportivo Cali after the Colombians were beaten 2-0 by Lanus.
In Asuncion, Cerro Porteno needed just two minutes to take the lead at the Estadio General Pablo Rojas.
Daniel Guiza scrambled in the opener after a shot cannoned off the crossbar and into his path.
It was 2-0 after eight minutes as Julio dos Santos calmly tucked a penalty into the bottom corner to put his side in control.
O'Higgins struck with a penalty of their own on 10 minutes as Pablo Calandria converted a spot-kick, but they were unable to find an equaliser.
Argentina's Lanus also made a blistering start to set up their crucial victory over Deportivo Cali at the Estadio Ciudad de Lanus – Nestor Diaz Perez.
Jorge Pereyra Diaz got a touch on Maximiliano Velazquez's cross from the left, and it was enough for his effort to sneak past Faryd Mondragon.
They doubled their lead in the fifth minute as Velazquez turned from provider to scorer in stunning fashion.
The left-back received a corner from Victor Ayala before unleashing a 30-yard effort into the top corner, leaving Mondragon unmoved.
Paolo Goltz struck the crossbar with a late penalty, but it mattered little as Lanus claimed a vital three points.
In Group 9, Brazilian side Atletico Paranaense made it three wins from as many games with a comfortable 3-0 win over Peru's Universitario.
Union Espanola jumped to second in Group 2 after a 1-0 win over San Lorenzo and Defensor Sporting came from behind to deny Cruzeiro in a 2-2 draw.
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