"Possibly there are officials and some high-level people involved," Martinez said. "We are going to get to the bottom of it."
He said the investigation is separate from the one started by the local federation, which on Wednesday said the players who participated in the suspect matches will be suspended for 30 days while the allegations are investigated.
"This is not a punishment, these are provisional, precautionary measures," Federation President Carlos Mendez Cabezas said.
CONCACAF, the sport's continental governing body, said it was "deeply saddened" by the "claims of match manipulation."
"The confederation fully supports the football federation of El Salvador and other pertinent organizations involved in the above mentioned investigation and hopes for a fair due process in order to determine the validity of these accusations," it said in a statement.
The regional body added that the fight against match-fixing was paramount.
"It is our duty to fight against organized crime alongside all stakeholders involved," CONCACAF said.
Mendez Cabezas said the games under scrutiny include El Salvador's 5-0 Gold Cup loss to Mexico on July 5, 2011, as well as a 2-1 loss to the United States on Feb. 24, 2010, a 1-0 loss to D.C. United on July 19, 2010, and a 4-1 loss to Paraguay on Feb. 6, 2012.
He said FIFA has been notified so that the suspensions could be extended internationally. He also said El Salvador will play no more games until the probes into the matches are completed.
Martinez said he has already sought collaboration from authorities in other countries where match fixing has taken place.
The suspended players are: Mardoqueo Henriquez, Luis Alonso Anaya, William Osael Romero, Ramon Alfredo Sanchez, Christian Castillo, Eliseo Quintanilla, Jose Miguel Granadino, Miguel Montes, Dagoberto Portillo, Rodolfo Zelaya, Victor Turcios, Carlos Romeo Monteangudo, Dennis Alas, Jose Alfredo Pacheco, Marvin Gonzalez, Carlos Carrillo, Darwin Bonilla, Rodrigo Alejandro Martinez, Reynaldo Hernandez Villeda, Ramon Flores, Benji Villalobos and Emerson Umana.