Shares in Merck, the German drugs and chemicals firm, have fallen in the wake of boss Bernhard Scheuble's departure from the firm.
Cancer treatment Erbitux has proved a success for Merck
Merck announced Dr Scheuble's immediate exit from the company on Tuesday after the German stock market closed, giving no reason for his departure.
Analysts said Dr Scheuble may have had a disagreement with the Merck family over the firm's future strategy.
Merck shares were down 2.11 euros, or 2.8%, at 71.55 euros by mid-afternoon.
Dr Scheuble had worked for Merck for 23 years, serving five years as chief executive.
Analysts said the company's recent performance had been strong, due in part to a recovery in its liquid crystals unit which produces components for flat screen TV and mobile phone displays.
"Given the suddenness of his departure, we would surmise that Dr Scheuble had a falling-out with the Merck family," investment firm Nomura said in a report.
"This is unlikely to have been over the current performance of the company, which is good, so we assume that the root cause was a disagreement over Merck's future strategy."
The Merck family hold a controlling 73% stake in the business, most widely known for its treatments for cancer, heart disease and diabetes.
Dr Scheuble has been succeeded by vice-chairman Michael Roemer.