Mark Gonzalez doubled the advantage with a precise free-kick in the 74th minute, before Sanchez made it 3-0 four minutes later. Sanchez added his second one minute before half-time and his goal-scoring antics earned him a strong challenge from midfielder Ignacio Garcia who was subsequently sent off.
Marcelo Bielsa's side now have 26 points, one less than leaders Brazil and two ahead Paraguay. Brazil beat Paraguay 2-1 in Recife.
Elsewhere, Venezuela and Uruguay drew 2-2 at Cachamay stadium. Giancarlo Maldonado opened the scoring after eight minutes, but Luis Suarez finally brought the Uruguayans level on the hour mark.
Ten minutes later Atletico Madrid's Diego Forlan put Uruguay ahead, but their lead lasted just three minutes as defender Jose Manuel Rey grabbed a point for Venezuela with a powerful free-kick from 25 meters. The result meant Ecuador moved into fifth place following their 2-0 victory over Argentina. They now have 20 points, two more than Uruguay and three ahead of Venezuela.
Finally, in Medellin hosts Colombia beat bottom-side Peru 1-0 to keep them in with a slim chance of reaching fifth place and the play-off. River Plate striker Radamel Falcao Garcia netted the only goal of the match in the 24th minute.
It was the first competitive Colombian goal in 210 minutes, as well as Falcao's first official goal with the national side. Colombia are three points behind fifth-placed Ecuador.
