Butt was also found guilty of conspiracy to accept corrupt payments. Jurors are still deliberating whether Asif was guilty of the same charge.
Both men denied the charges.
They will be sentenced later this week. Butt faces up to seven years in jail or a fine, and Asif a maximum of two years.
The three were accused of conspiring with a UK-based sports agent, Mazhar Majeed, to fix parts of the Pakistan-England Test Match in August 2010.
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An undercover reporter for the former News of the World newspaper recorded Majeed saying he could arrange for Pakistani cricket players to rig matches in exchange for large sums of money, thereby allowing co-conspirators to make huge winnings on bets.
Majeed was filmed accepting £150,000 ($240,000) in cash on the promise that Asif and Amir would deliver three no-balls at agreed points in the match. As captain, Butt also had to be in on the fix.
Both Majeed and Amir pleaded guilty to involvement in the scam last month.
Amir claimed that he was put under “extreme pressure” to bowl two no balls at Lord's, and that he was threatened to take part in the conspiracy, and that not doing so woud have serious implications for his career, the Cricketer reports.
Yawar Saeed, manager of the Pakistan team at the time of scandal, said Tuesday that the players had brought shame on their country:
"I’m very sad that this beautiful game of cricket has had to see this day. [...] I’m also sad because the country’s name has been dragged into this entire controversy. Pakistan is known for its talented players but this case has stained the country’s image badly."
Saeed resigned as manager following the controversy, Agence France Presse states.
All three players have been banned from playing for at least five years by the International Cricket Council.
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