ROBERT BARRLONDON (AP) â¿¿ Cynthia Carroll will step down as chief executive of mining company Anglo American PLC after almost six years in the job, the company announced Friday. Carroll, who is to leave the company as soon as a successor is found, made no reference to reports that some investors had lost faith in her leadership following a series of controversial events including a series of strikes in South Africa and a dispute in Chile. Earlier this month, the rating service Standard & Poor's lowered its outlook on the company from "stable" to "negative" because of the turmoil in South Africa. "Of course, we always listen to our shareholders very carefully. However, today's decision is very much based on Cynthia's decision," Anglo's chairman John Parker said in a video interview posted on the website Cantos. Anglo American shares rose about 3 percent to 1913 pence by early afternoon in London as investors hoped the change in leadership would benefit the company. "It will lead to speculation about a potential restructuring of the business or takeover," said Jonathan Jackson, an analyst at Killik & Co. in London. Carroll, a 55-year-old American, was appointed chief executive in 2007. She was the first non-South African and first woman to lead the company. "It is a very difficult decision to leave, but next year I will be entering my seventh year as chief executive and I feel that the time will be right to hand over to a successor who can build further on the strong foundations we have created," she said. Trained as a geologist, Carroll started her career with Amoco. She joined Alcan in 1989, rising in 2002 to the posts of president and chief executive officer of Alcan's primary metals group. Carroll will also be stepping down from her roles as chairman of De Beers, an appointment announced earlier this month, and of Anglo American Platinum.