An investigation is under way into allegations that two Fifa officials offered to sell their votes to one of England's competitors in the race to host the 2018 World Cup.

The Sunday Times claimed to have caught Nigerian Amos Adamu, a Fifa executive committee member, on film as he told an undercover reporter he would guarantee his vote in exchange for £500,000.

The newspaper's reporters had posed as lobbyists for a consortium of private American companies which wanted to help secure the World Cup for the United States.

The US pulled out of the race on Friday, saying it wanted to focus on bidding for the 2022 tournament. The reporters involved in the story emphasised they had no links to the bid and that the US committee's campaign had been completely above board.

At an initial meeting in London with Adamu, also president of the West African Football Union, he is said to have told the reporters that he wanted money to build four artificial football pitches in his home country.

The newspaper said a second member of the committee, Reynald Temarii, who is president of the Oceania Football Confederation, asked to be paid for his vote as well. In his case, they said he wanted the money to finance a sports academy.

Fifa has asked for all material relating to the allegations.

A spokesman said: "Fifa and the Fifa Ethics Committee have closely monitored the bidding process for the 2018 and 2022 Fifa World Cups and will continue to do so.

"Fifa has already requested to receive all of the information and documents related to this matter, and is awaiting to receive this material.

"In any case, Fifa will immediately analyse the material available and only once this analysis has concluded will Fifa be able to decide on any potential next steps.

England is one of four bids still in the running for the 2018 World Cup alongside Russia and joint bids from Belgium-Holland and Spain-Portugal.