Story highlights Google CEO Larry Page "lost his voice," won't be speaking at company's conference this week

But Google has offered few details, leading to speculation about "mystery illness"

Some analysts and tech reporters have criticized the company's silence on the matter

Google will kick off its annual I/O developers' conference Wednesday in San Francisco, but CEO Larry Page won't be speaking there. He also was a no-show at Thursday's annual stockholders meeting and is expected to miss the company's quarterly earnings call next month.

Left to explain Page's unexpected absence at the shareholder's meeting, Google Executive Chairman Eric Schmidt told attendees that Page had "lost his voice" and "can't do any public speaking engagements for the time being."

In an e-mail to employees the same day, Page wrote, "there is nothing seriously wrong with me," a person familiar with the matter told the Wall Street Journal

The company issued a statement Thursday saying, "Larry has lost his voice. This means he can't do any public speaking engagements for the time being, including today's shareholder meeting, I/O next week and our earnings call in mid July.

"Larry will, of course, continue to run the company and he will be involved in all the strategic business decisions we make."

There is no evidence that Page, who has long been reluctant to speak in public, is seriously ill. But four days later, Google has had nothing else to say on the matter, and analysts and bloggers are getting restless. News sites have speculated about Page's "mystery Illness," and Google's stock has been trending down since late last week.

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"We have no specific reason to think there is anything more to Larry's condition, but we find it odd that the company would already rule him out of the 2Q call, which is likely still a few weeks away," said Doug Anmuth, an analyst at JP Morgan. "We think this could raise some questions among investors."

"We have absolutely no idea what is going on," said CNNMoney's assistant managing editor, Paul R. La Monica, in a video report Monday. "We can only hope that it's nothing serious, maybe just a really bad case of laryngitis, and he's under doctor's orders not to speak."

Observers point out that while Page's health may be a private matter, Google is a publicly traded company.

"There shouldn't be any mystery (here)," La Monica added. "Google should own up to whatever it is. ... It could stop, maybe, any rumors from going around."

The health of a tech giant's CEO may bear extra scrutiny at a time Silicon Valley is still recovering from the death last fall of Apple chief Steve Jobs. Many investors and others criticized Apple for failing to disclose details about Jobs' condition.

Page, 39, is one of Google's two co-founders and took over as CEO last year after Schmidt became chairman.

"Not being able to speak hardly puts someone on the same path as Steve Jobs, nor does it keep him from making key decisions or pointing his company in the right direction. It's also possible the full extent of what's ailing him isn't known," wrote Jena McGregor on Monday in the Washington Post

But "more specific information could calm any rattled nerves of investors, keep customers from worrying, and stop remote diagnoses from being offered in the press," she added. "More than likely, the matter would cease to be an issue: Everyone would say "get well soon," and move on."