Apple’s CEO, Steve Jobs, is taking medical leave for the second time in as many years, sending the company’s shares tumbling close to 10 percent on revived concerns about the long-term future of the iPhone- and iPad-maker.

The news, disclosed early on a U.S. holiday when markets were closed, came nearly two years to the date after Jobs first took a six-month break to undergo a liver transplant.

“At my request, the board of directors has granted me a medical leave of absence so I can focus on my health,” Jobs, 55, wrote in an e-mail to staff released in a press release. “I love Apple so much and hope to be back as soon as I can.”

Unlike the previous announcement, Apple did not specify any timeline for Jobs to resume his duties. An Apple spokesman declined to comment further.

Analysts said investors would likely fear the worst about Jobs’ health, and expected Apple to remain tight-lipped about his condition.

Jobs, a survivor of pancreatic cancer, said chief operating officer Tim Cook would take responsibility for day-to-day operations — but he would continue to be chief executive officer and be involved in major strategic decisions.

Apple shares closed 6.2 percent lower in Frankfurt. Apple’s destiny has been closely tied to Jobs, who revived the computer maker’s fortunes in 1996 after a 12-year absence from the company he co-founded. reuters