Newell's fans lit the flares as their team crushed Nacional of Uruguay 4-0 at the Marcelo Bielsa in Rosario in a Group Six match two weeks ago and Chilean referee Enrique Osses halted play for a minute while the smoke cleared.
"The disciplinary tribunal continues to show perseverance in imposing the CONMEBOL's rules with the intention of eradicating from our stadiums the use of flares and other artefacts that could be a danger to the attending public," the Asuncion based body said in a statement.
A teenage Bolivian fans was killed by a firework launched by supporters of visiting Brazilian side Corinthians, then the holders, during a group match in the Bolivian city of Oruro last year in the worst such incident.
Newell's visit Gremio in Porto Alegre on Thursday in their next match in Group Six, which the Brazilian side lead with six points from two matches.
Atletico Nacional of Colombia have four points, Newell's three and Uruguay's Nacional one.
Brazilian sides did not fare too well on Wednesday with Botafogo losing 2-1 away to debutants Independiente del Valle of Ecuador at high altitude in a Group Two match in Quito.
The match was level at 1-1 with a quarter of an hour to go when Botafogo had defender Bolivar, who had scored an equaliser, and Edilson sent off in the space of one minute, and they conceded an added-time winner scored by Junior Sornoza.
Holders and Group Four leaders Atletico Mineiro were held 2-2 by Paraguay's Nacional in Asuncion.
Flamengo, South American champions in 1981, dropped two points in a 2-2 draw at home to Bolivar of Bolivia at the Maracana in Group Seven.
- Sports & Recreation
- Marcelo Bielsa