Many of Google's services, including search and Gmail, are currently offline in China without any clear indication of the cause. In a statement given to both Reuters and Bloomberg Businessweek, Google said that "we've checked and there's nothing wrong on our end." However, a quick look at Google's Transparency Report site shows a rapid and uncharacteristic traffic dip this morning that hasn't yet recovered (though it's worth noting that we're in the time of day where traffic from China is typically low). A quick look at the tracking site Great Firewall of China corroborates Google's Transparency Report — a number of Google subdomains are currently inaccessible. Unfortunately, such outages aren't unheard of, with Google being blocked in China back in 2010 when the company said it would stop filtering its search results for Chinese users. We'll be watching to see whether technology, politics, or some combination of the two is behind today's outage.
Update: The Google services outage in China looks to have been a short-lived one. The company's Transparency Report shows that traffic returned to normal levels around 6AM ET, this morning, though it's still unclear what exactly caused users in China to lose access.