Fifa, football's governing body, has been hit by two corruption inquiries. Seven Fifa officials have been arrested in Switzerland at the request of the US authorities after a total of 14 people were indicted for corruption. The amounts involved are alleged to be above $150m (£97m).
Hours later, the Swiss authorities launched their own criminal inquiry into the bidding process for the 2018 and 2022 World Cups. Swiss police raided Fifa's headquarters in Zurich and seized electronic evidence.
Why does this matter?
Fifa is the body responsible for running world football. In recent years it has been dogged by accusations of corruption, particularly the award of the 2022 World Cup to Qatar. In December 2014, Fifa chose not to release its own investigation into corruption - which it says exonerates the bidding process. The report's author, American Michael Garcia, resigned.
The World Cup is one of the biggest sporting events in the world and generates billions of dollars in revenue. These arrests and investigations cast doubt over the transparency and honesty for the process of allocating the last three tournaments.
The two inquiries
The American indictments - which focus on corruption allegations going back to 1991 - are the most serious, as they could potentially lead to prison terms. As well as the seven people arrested in Zurich, indictments were issued for seven others.
The Swiss criminal case is still at the investigative stage but could provide revelations about the allocation of the forthcoming World Cups. It is the first time that authorities with the power to prosecute have looked at the bids.
However, in their statement the Swiss make it clear that Fifa are actually the "injured party". This means that they are investigating individuals who might have abused the bidding process and used it for money laundering.
Who's accused of corruption?
The most senior figures arrested at the request of US authorities are football powerbrokers in North America, Latin America and the Caribbean.
They are connected to Concacaf (the Confederation of North, Central America and Caribbean Association Football), which is part of Fifa - essentially it is in charge of football in that region. One of its key roles is helping to agree World Cup TV and sponsorship deals in the US.
Jeffrey Webb is the head of Concacaf and was widely seen as being groomed as a successor to Fifa president Sepp Blatter - indeed, Mr Blatter had said as much. His predecessor Jack Warner has also been indicted. Mr Webb replaced Mr Warner after he was forced to step down after a fraud inquiry.
Latin American football chiefs also figure heavily in the list. There are two former presidents of CONMEBOL, which represents South American football nations. One of them, Eugenio Figueredo, was a Fifa vice-president - one of the most senior roles in world football.
A key figure appears to be Charles "Chuck" Blazer, US soccer's former representative to Fifa, who has become a supergrass for the FBI. He has pleaded guilty and already repaid $1.9m, with a further amount to be determined at the time of sentencing.
Has Sepp Blatter been arrested?
No.
The Fifa president and most powerful man in football is not named in the US indictments. However, they do say those arrested were working as part of Fifa - of which he is head. He has so far refused to step down despite growing pressure, saying he would stay on to "lift the shadow" cast by the arrests.
Mr Blatter was recently forced to deny reports that he was avoiding travelling to the United States because he feared arrest.
Why were the officials arrested?
The FBI has been investigating Fifa for the past three years. The investigations were initially sparked by the bidding process for the Russia 2018 and Qatar 2022 World Cups, but was widened to look back at Fifa's dealings over the past 20 years.
The Department of Justice's indictment says that the corruption was planned in the US, even if it was then carried out elsewhere.
The use of US banks to transfer money appears to be key to the investigation.
Why Switzerland?
It is the home of Fifa, with the company's registration as a charity allowing it to pay little tax.
Switzerland might be perceived as a country where less than transparent companies are welcome, particularly when it comes to tax, but
its extradition agreement with the US is clear that it will hand over people for criminal acts.
It appears that US authorities took advantage of the fact that Fifa's annual Congress brought together key suspects in an extradition-friendly country.
How much money is involved?
Massive amounts, allegedly.
The US indictment alleges over $150m in corruption, and that does not include other possible corruption around the world. An earlier Fifa report into Caribbean corruption, which was leaked, alleged that bribes of
$40,000 were handed to officials in cash-stuffed envelopes.
Fifa makes nearly all its revenue from the World Cup, the most lucrative sporting event in the world, eclipsing even the Olympics.
Last year's tournament cost the host country Brazil an estimated $4bn, and yet Fifa made more than $2bn in profit. The costs of the next two World Cups are expected to dwarf this: Qatar 2022 is reported to be above $6bn.
Just bidding for the right to host the World Cup is enormous - the English FA spent £21m on its failed bid for the 2018 tournament.
Will the Russia 2018 or Qatar 2022 World Cup be moved?
Unlikely but not impossible at this point.
The US indictments focus on historical corruption - the selection of South Africa as the 2010 World Cup host is mentioned - but not the forthcoming world cups. The Swiss investigations into those tournaments might prove more fruitful, but it would take overwhelming evidence to run the bidding process again.
Practically, moving the 2018 Russia World Cup would be fraught with difficulty. Very few countries have the stadiums, infrastructure or money to host the event at such short notice. Even most English stadiums would need a major refurbishment to meet Fifa standards. Germany offers the best option, having hosted the 2006 World Cup.
Qatar is far more vulnerable and has been dogged with controversy and allegations of corruption ever since its award. However, having seen out several corruption scandals, an unprecedented move from a summer to winter tournament and a scandal over the treatment of migrant workers, the odds are it will somehow hold onto football's most illustrious competition.