El Salvador's national football team say they have refused a bribe to fix Tuesday's World Cup 2018 qualifying game against Canada.
At a news conference, team members played an audio recording of the person allegedly offering various incentives.
Canada must beat El Salvador - who cannot qualify - in Vancouver, and hope Mexico defeat Honduras in the final round of Group A games to stand a chance of progressing.
Fifa confirmed it is investigating.
"It's the most dramatic thing in football I've seen for some time" investigative journalist Declan Hill told the BBC World Service. "The entire team came in with their coaches and said they had been approached on Saturday.
"They played an 11-minute conversation with the attempted match-fixer. He was offering each player a variety of money per minute depending on the result they could get. The most they would have got for allegedly fixing the match would have been about $3,000 per player."
Hill said the offer was allegedly made by an El Salvadorian who knew some of the players, but who wanted to aid the Honduras national team.
The BBC has approached the Honduras football association for comment.
A Fifa spokesman said it is "aware of the claims" and that "in co-operation with the respective organisations and authorities, Fifa is looking into this matter".
Canada, El Salvador, Honduras and Mexico are members of the Confederation of North, Central America and Caribbean Association Football (Concacaf).
Three Concacaf nations will automatically qualify for the 2018 World Cup, which is being staged in Russia, with a fourth entering a play-off against a team from the Asian Football Confederation.
At a news conference, team members played an audio recording of the person allegedly offering various incentives.
Canada must beat El Salvador - who cannot qualify - in Vancouver, and hope Mexico defeat Honduras in the final round of Group A games to stand a chance of progressing.
Fifa confirmed it is investigating.
"It's the most dramatic thing in football I've seen for some time" investigative journalist Declan Hill told the BBC World Service. "The entire team came in with their coaches and said they had been approached on Saturday.
"They played an 11-minute conversation with the attempted match-fixer. He was offering each player a variety of money per minute depending on the result they could get. The most they would have got for allegedly fixing the match would have been about $3,000 per player."
Hill said the offer was allegedly made by an El Salvadorian who knew some of the players, but who wanted to aid the Honduras national team.
The BBC has approached the Honduras football association for comment.
A Fifa spokesman said it is "aware of the claims" and that "in co-operation with the respective organisations and authorities, Fifa is looking into this matter".
Canada, El Salvador, Honduras and Mexico are members of the Confederation of North, Central America and Caribbean Association Football (Concacaf).
Three Concacaf nations will automatically qualify for the 2018 World Cup, which is being staged in Russia, with a fourth entering a play-off against a team from the Asian Football Confederation.
