Criminal proceedings have been opened against former Fifa secretary general Jerome Valcke, Swiss investigators say.
Valcke was put on leave last September after football's governing body said it had "been made aware of a series of allegations" involving him.
The 55-year-old Frenchman was later banned from football for 12 years.
The Office of the Attorney General of Switzerland (OAG) said it is now investigating Valcke for "various acts of criminal mismanagement".
It added the criminal investigation related to the "matters investigated by the Fifa Ethics Committee" which led to Valcke's ban last month.
He has not been arrested but was questioned by investigators who carried out searches on Thursday.
Valcke was sacked by Fifa after it investigated allegations of misconduct relating to sales of World Cup tickets.
His lawyer said his client had done "absolutely nothing wrong".
But the inquiry heard as well as his involvement in the World Cup tickets sales, from which he allegedly sought to privately benefit, he also attempted to sell TV and media rights to a third party in a cut-price deal.
The inquiry also heard Valcke routinely used a private plane for personal use "and caused considerable financial damage to Fifa".
Fifa finances revealed
The Swiss attorney general's statement came on the day it emerged Valcke was paid 2.1m Swiss francs (£1.5m) by Fifa last year.
The organisation's annual financial report also showed disgraced former president Sepp Blatter earned 3.63m Swiss francs (£2.59m).
The salaries were released for the first time as part of new Fifa president Gianni Infantino's commitment to transparency.
Infantino was elected last month with a mandate to clean up the corruption-plagued body.
The financial report also showed Fifa lost $122m (£84m) last year.
"These results stand as a cautionary tale of what can happen if we lose sight of the primary responsibilities of our mission, and if we fail to take the necessary steps to protect our organisation against wrongdoing," said Infantino.
"Fifa's healthy financial reserves, built up when the sun was shining as a prudent insurance against unforeseen risks, have served to further stabilise the organisation, and to give us the breathing space we need to put things right.
"This strong financial position overall means we are more than capable of weathering the current storm."
Blatter appeals against Fifa ban
Blatter, 80, was Fifa president from 1998 until being forced to stand down last year. He was found guilty by Fifa of ethics breaches over a $2m (£1.3m) "disloyal payment" to former Uefa head Michel Platini.
He was subsequently given a six-year ban from football.
On Thursday it was confirmed the Swiss has now taken his appeal to the Court of Arbitration for Sport (Cas).
Platini, who was also banned for six years, launched his own appeal bid with Cas last month.
Both men deny wrongdoing. They claim the payment, made in 2011, related to a gentleman's agreement made in 1998 for work carried out by the Frenchman when he was a technical advisor for Blatter.