"With reference to the health of Sergio Marchionne, FCA communicates with profound sorrow that during the course of this week unexpected complications arose while Mr. Marchionne was recovering from surgery and that these have worsened significantly in recent hours", the company said in a statement today.
Marchionne had stated his intention to retire in 2019, but his exit a full year earlier and the tone of various statements released by FCA indicate that the former CEO's health may be in steep decline.
The boards of Fiat Chrysler, Ferrari and CNH Industrial were called to urgent meetings Saturday in Italy in light of executive Sergio Marchionne's surgery and prolonged convalescence.
Fiat Chrysler Automobiles NV's European chief has resigned after being passed over to replace ailing Sergio Marchionne as chief executive officer of the group, according to people familiar with the matter.
Marchionne's biggest coup will be seen as the merger with the then moribund Chrysler Group, which had just emerged from Chapter 11 bankrupcy in 2009 when Fiat, along with the United Autoworkers Union and the Canadian Government were the major investors.
His departure also vacates the positions of Ferrari CEO and chief executive, with Agnelli family progeny John Elkann picking up the reigns as CEO and Louis Camilleri taking the job of chief executive. Analysts estimate that Jeep alone could be worth the entire market value of Fiat Chrysler.
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By 0714 GMT, FCA shares were down 3.6 percent, Ferrari down 4.6 percent, CNH Industrial down 3.7 percent, while Exor, the investment holding of the Agnelli family that controls all three companies, was trading down 3.8 percent.
The premium brand is also key to a five-year FCA plan unveiled by Marchionne in June to increasingly focus on hybrid and electric vehicles.
The passenger-car brands of Fiat and Chrysler have been less profitable.
Marchionne's tenure also has been controversial at times.
Marchionne took over as president of Ferrari in 2014 from Luca Di Montezemolo, who served more than 20 years in the role. He created shareholder value for the Fiat-founding Agnelli family with successful spinoffs of Fiat's heavy vehicle maker CNH Industrial and of the iconic Ferrari super sports auto company.
On the eve of the running of the F1 Grand Prix in Germany on Sunday, Mercedes head of motorsport Toto Wolff expressed concern about his rival Marchionne.
"This is a very important person for Formula 1", said Mercedes team principal Toto Wolff.