Facebook shares have risen above the $38 flotation level for the first time since they began trading in 2012.

The world's largest social networking site saw its price rise as high as $38.31 in morning trading, before falling back to close at $36.80.

The company's shares have been boosted since the company reported stronger-than-expected earnings on 24 July.

Investors have been encouraged by the fast growth of Facebook's mobile advertising revenue.

It now derives 41% of its total ad revenue from mobile.

Facebook's flotation in May 2012 got off to a disastrous start as shareholders took fright over the company's apparent lack of mobile strategy and slowing revenue growth.

Some accused founder Mark Zuckerberg of overhyping the company's growth forecasts.

Just three months after the flotation, the share price had collapsed to about $18, wiping $48bn off the company's stock market value.

But the company's recent forecast-beating results have helped restore investor confidence.