Something incredibly suspicious is going on with the stocks in China's richest man's solar power company

There's something incredibly dodgy going on in a major Chinese stock - the price is going through the roof, but only in the last ten minutes of the day.

The amazing investigation into the Hanergy Thin Film Power Group comes from the Financial Times, and couldn't sound any more suspicious.

The firm is involved in thin film technology for solar power. It's a growing industry, but Hanergy's growth has been astonishingly rapid. It's made company chairman Li Hejun China's richest man, according to Forbes.

But there are some issues.

In short, the share price has surged in recent years, spiking by thousands of percent and turning any early investments in the firm into massive cash piles. But pretty much all of the increase has happened just before trading closes.

Here's the FT's Miles Johnson and Gavin Jackson explaining just how severe the end-of-day spike in shares is:

A Financial Times analysis of two years of trading data of Hanergy Thin Film stock - more than 800,000 individual trades on the Hong Kong Stock Exchange - shows that shares consistently surged late in the day, about 10 minutes before the exchange's close, from the start of 2013 until February this year...

It means that an investor who held HTF shares from the start of trading at 9am to 3.30pm would have lost money - despite the company's share price rising by 1,168 per cent between January 2013 and February 9 2015.

A trader who bought HK$1,000 ($129) worth of HTF at 9am on every day of trading since January 2 2013 and sold those shares at 3.30pm each day, would have seen their money shrink to HK$635 by February 2015. But if they held on for just under half an hour more each time, the HK$1,000 would have turned into HK$8,430. This calculation does not include overnight gains.

Hanergy's explosion over recent years has been absolutely astonishing - the stock's value has risen by more than 1,800% since the beginning of January 2013 to now.

Here's how it looks:

When comparison to Hong Kong's Hang Seng index (on which Hanergy is not listed), the index is barely visible at all.

The FT spoke to several experts who discussed whether the spike at the end of a trading day was likely to be the work of manipulation, or there was some other explanation. Here's one example:

Rajesh Aggarwal, professor of finance at Northeastern University in Boston and an expert on stock market manipulation cases, also reviewed the FT findings and raised the spectre of manipulation: "This is consistent with the stock price having been systematically manipulated over the past couple of years. This pattern of large price increases during the last 10 minutes of trade is extremely unlikely to have occurred randomly."

Earlier this month, Hanergy shares slumped after the Hong Kong exchange asked Hanergy for an explanation of its sudden price surges, which it didn't provide.