Criminal proceedings were opened against Blatter last September for suspected financial mismanagement over a payment he approved from Fifa funds for Michel Platini in 2011.

The Swiss attorney general's office said: "Documents were seized in connection with the suspected payment."

Blatter and Platini were both banned from football for six years after an investigation by Fifa's ethics committee.

They deny wrongdoing and are appealing to the Court of Arbitration for Sport.

Blatter and Platini have constantly denied wrongdoing and claimed they had a verbal deal for additional salary that former France great Platini would receive for working as Blatter's presidential adviser from 1999 to 2002.

Before the £1.3 million payment was revealed in September, Platini had been the leading candidate to succeed Blatter as president in Fifa's emergency election on February 26

The payment emerged during a wider investigation led by Switzerland's attorney general, Michael Lauber, of Fifa business.

The investigation includes suspected money laundering in the 2018 and 2022 World Cup bidding contests.

Platini's status in the Swiss investigation is "between a witness and an accused person", Mr Lauber has said.

The case against Blatter also involves alleged misappropriation of Fifa funds during his more than 17 years as president, which formally ended two weeks ago.

He allegedly arranged an undervalued deal for 2010-14 World Cup broadcast rights for the Caribbean with former Fifa vice president Jack Warner.

Platini has previously said he asked Blatter for a salary of a million Swiss francs when approached in 1998 to work for the newly elected president.

Blatter said there was a contract for 300,000 Swiss francs, the same as Fifa's then secretary general in line with its salary structure, plus a "gentleman's agreement" to get the rest later.

Swiss law obliged Fifa only to pay the deferred money within five years. It was not until 2010 that Platini, by then president of the governing body for European football and a Fifa vice president, reportedly asked for the balance, and was paid in February 2011.

That timing has raised suspicion as the payment came during a Fifa presidential election campaign. Uefa later urged its members to support Blatter - who promised them it would be his final term - against Mohamed bin Hammam of Qatar.

Blatter won that 2011 election unopposed after bin Hammam was implicated in bribing Caribbean voters. From then on, Platini was the likely successor to lead Fifa.

Instead, Platini's long-time right-hand man at Uefa, general secretary Gianni Infantino, won the Fifa presidential election last month.