Image copyrightGetty ImagesMicrosoft has confirmed that access to its Bing search engine in China has been restored after an outage.

The firm did not offer any explanation for why the search engine had been inaccessible.

The outage caused concern that the service might have been blocked by the Chinese authorities.Authorities in China operate a firewall that blocks many US tech platforms, including Facebook and Twitter."We can confirm that Bing was inaccessible in China, but service is now restored," Microsoft said it a statement.

China-based censorship monitoring group GreatFire says the outage was unlikely to be government-related.

GreatFire tests whether URLs are accessible in China, and to what extent their domains show evidence of censorship.The group says Bing China is hosted in China on Chinese servers, which means it's already subject to local censorship directives.

The government's internet censorship regime, often known as the "Great Firewall", uses a series of technical measures to block foreign platforms and controversial content.Chinese authorities have also cracked down on Virtual Private Networks, which allow users to skirt around the firewall.China-based messaging services and social media are restricted, with key words and expressions blocked if they express dissent or ridicule senior political leaders.Microsoft has continued to operate in China, even as many other US tech companies have been blocked or have pulled out.Facebook, Twitter and Google are all blocked on the mainland.

Google shut down its search engine in China in 2010, after rows with the authorities over censorship and hacking.Bing has a small market share among search engines in China, where locally-grown Baidu dominates the market.