Football fans across the Arab world were furious when they tried to watch the opening game of the World Cup in South Africa and found the signal was blocked.
Al Jazeera Sport, the network with exclusive broadcasting rights for the tournament in the Middle East and North Africa, has said its signal was deliberately jammed on satellite channels Nilesat and Arabsat in an "act of piracy".
Viewers were faced with blank or frozen screens when they tried to watch the opening game between Mexico and South Africa on Friday.
Al Jazeera's signal returned in the second half of the match, but the quality was patchy.
Some commentary for the game also appeared in the wrong language.
"We apologise for the interruption that happened, it was because of satellite interference from an unknown source," Nasser al-Kholeifi, the managing director of Al Jazeera Sport, said.
He said he was astonished that the World Cup signal was blocked because it was "not a political programme, but a sporting event.
"We will do whatever we can to find whoever was responsible," al-Kholeifi said.
Nilesat, the Egyptian satellite company, said it is investigating the source of the jamming.
It pledged to "take all measures necessary against such an irresponsible act that violates all international laws and norms".
Nilesat and Al Jazeera Sport are also "looking into broadcasting the Al Jazeera channels airing World Cup games on more than one frequency on Nilesat to ensure the visibility of the games".
Fifa, the international body which organises the World Cup, said it was "supporting Al Jazeera in trying to locate the source of the interference" in the broadcast.
In a statement on Saturday, Fifa said it "is appalled by any actions to try to stop Al Jazeera's authorised transmissions of the Fifa World Cup as such actions deprive football fans from enjoying the world game in the region".
Al Jazeera Sport has, meanwhile, promised to pursue legal action over the incident.
"After months of negotiations with Fifa, we want our Arab viewers to enjoy a few of the World Cup events for free," al-Kholeifi said.
"But sadly, there are some people who have political agendas to the contrary. We will do our utmost to find who was behind it."
Friday's transmission disruption upset football fans across the Middle East, in places as far apart as the Gaza Strip and Baghdad.
"What happened is shameful. The World Cup only happens every four years," one football fan in the Palestinian coastal territory said.
"We were in a coffee shop and we tried to find another place and they had the same problem."
Another viewer in Gaza said: "We have lost our patience for this mistake. We are waiting to watch the only Arab team, Algeria."