Image copyright Parry family Image caption Eloise Aimee Parry, 21, from Shrewsbury, died in hospital in April 2015 after taking diet pills believed to have contained DNP

Around 19 websites believed to be selling diet products containing a chemical linked to a series of deaths in the UK have been closed down.

The Food Standards Agency said the websites selling 2,4-dinitrophenol (DNP) were shut down in the last year.

But a BBC investigation has found hidden sites on the so-called dark web were still selling the products.

DNP is an industrial chemical licensed for commercial use but not for human consumption.

'No safe dose'

In April 2015, Eloise Aimee Parry, 21, from Shrewsbury took diet pills she had bought over the internet. Later that day she was dead.

Sean Cleathero died in October 2012 aged 28, after taking an illegal slimming pill in High Wycombe, Buckinghamshire.

His mother Sharon Ayres, said: "Why would people still want to take it anyway, whether they think there is a safe dose, because there isn't a safe dose?"

Former Prime Minister David Cameron raised the issue in the Commons following the death of Sarah Houston who died in Leeds in 2012 after she had taken pills containing DNP.

Image copyright Ross Parry Image caption Medical student Sarah Houston died in September 2012 after secretly taking slimming pills which contained DNP that she had bought online

The BBC investigation found a number of suppliers were marketing DNP as a diet product for human consumption.

A number of samples were bought online and sent for laboratory tests which found they contained about 40% DNP - a potentially lethal amount.

Jon Griffin, analyst for Kent Scientific Services at Kent County Council, said: "You're not being able to control your body temperature, at 40 per cent that danger rises significantly, this has got some potential in there for very serious repercussions.

"Worst case scenario would be death."

Image copyright Wikimedia Image caption 2,4-dinitrophenol or DNP is a highly toxic and industrial chemical

What is DNP?

2,4-dinitrophenol or DNP is highly toxic and is not intended for human consumption

An industrial chemical, it is sold illegally in diet pills as a fat-burning substance

Users experience a metabolism boost, leading to weight loss, but taking even a few tablets can be fatal

Signs of acute poisoning include nausea, vomiting, restlessness, flushed skin, sweating, dizziness, headaches, rapid respiration and irregular heartbeat

Consuming lower amounts over longer periods could lead to cataracts and skin lesions and impact on the heart, blood and nervous system

Experts say buying drugs online is risky as medicines may be fake, out of date or extremely harmful

The sale of DNP is the subject of an ongoing investigation involving police, Interpol and the Food Standards Agency

The Medicines and Healthcare Products Regulatory Agency (MHRA) seized £1.4 million worth of unlicensed dietary medicines in 2015-16, £960,000 more than two years before.

Lynda Scammell, senior policy manager at the MHRA, said: "The internet offers access to a vast number of websites offering products marketed as 'slimming' or 'diet' pills.

"Many of these pills will not be licensed medicines. That means their contents are unknown and untested.

Chances are they simply will not work, but they may contain dangerous ingredients," she said.

"The consequences for your health can be devastating."