Argentina lost their unbeaten record in 2010 World Cup qualifiers on Tuesday as Colombia took advantage of a first-half red card for Argentina's Carlos Tevez to win their match 2-1, while Venezuela hit back three times to beat Bolivia 5-3.
Dayro Moreno scored an 83rd minute winner for Colombia in Bogota after Manchester United forward Tevez was dismissed in the 25th minute for a petulant kick at Ruben Dario Bustos.
Venezuela, after clawing their way back three times to level with Bolivia, then scored twice in the last two minutes following an injury to visiting goalkeeper Carlos Arias.
The results opened up the single South American group, a marathon two-year contest in which each team plays 18 games.
Argentina stayed top with nine points from four games, while Colombia went second with eight and Venezuela moved on to six.
Bolivia, already struggling, have only one point.
The fourth match day will be completed on Wednesday when Brazil (5 points) face Uruguay (4), Ecuador (0) host Peru (2) and Paraguay (7) visit Chile (4).
The top four teams qualify directly for South Africa in 2010 and the fifth plays off against a team from the CONCACAF zone.
Despite Tevez's dismissal, Argentina went ahead in the 37th minute with an individual effort from Lionel Messi, who slipped past three defenders before flicking the ball past Agustin Julio.
Messi was also close again in the 51st minute before Colombia hit back when Bustos, for the second game in a row, scored with a brilliant free kick and Moreno finished off a break. Both scorers were booked for shirtless celebrations.
Venezuela and Bolivia shared four goals in the first half in San Cristobal as Marcelo Martins and Juan Carlos Arce twice put Bolivia ahead and Daniel Arismendi replied for the hosts.
Martins regained the lead for Bolivia in the 78th minute, putting them on the brink of winning a World Cup qualifier away from home for the first time in 14 years, but Alejandro Guerra pounced on poor defending to equalise in the 83rd minute.
Bolivia keeper Arias then appeared to pull a muscle but, with his team having made three substitutions, carried on even though he could barely walk.
In the 89th minute, Giancarlo Maldonado latched on to a chipped ball forward and headed the ball over Arias, who was slow off his line.
Arias then went off and was replaced in goal by left back Luis Gutierrez, who was caught off his line as Maldonado scored with a 30-metre chip in injury-time.