(Reuters) - CSX Corp's <CSX.O> shares tumbled on Friday in premarket trading after the No. 3 U.S. railroad said Chief Executive Hunter Harrison was taking medical leave for unexpected complications from a recent unspecified illness.
The leave comes amid the company's controversial turnaround plan that has drawn customer criticism and scrutiny from regulators. [nL1N1OF03H]
"The importance of Harrison's influence is immense," Baird Equity Research Benjamin Hartford wrote in a note. Harrison's health has been an ongoing concern among investors since his hiring, Hartford added.
A railroad legend, Harrison was hired as CSX's CEO earlier this year. He previously turned around Canadian National and Canadian Pacific Railway Ltd <CP.TO>.
James Foote, who was named CSX's chief operating officer in late October, was appointed acting CEO.
CSX's shares fell 10.3 percent to $51.42 in premarket trade. Up to Thursday's close, they had risen 15.8 percent since March when Harrison took the helm.
(Reporting by Arunima Banerjee in Bengaluru; Editing by Bernard Orr)