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Rhys Williams said news of the failed test had come as a "great shock" to him

Glasgow 2014 Commonwealth Games Dates: 23 July - 3 August Coverage: Live on BBC TV, HD, BBC Radio 5 live, Red Button, Connected TVs, online, tablets and mobiles

Welsh 400m hurdler Rhys Williams is out of the Commonwealth Games after failing a drugs test at the Glasgow Grand Prix on 11 July.

The Team Wales athletics co-captain says he is "devastated" and denies knowingly taking any banned substance.

The 30-year-old son of former Wales and Lions rugby player JJ Williams tested positive for both his A and B samples.

He is banned from all competition by UK Anti-Doping pending a hearing.

"As a professional athlete, I have always supported and have been an advocate of clean sport," said Williams, European champion in 2012.

Rhys Williams' medals 2006: 4x400m hurdles silver, European Championship 2010: 400m hurdles bronze, Commonwealth Games 2010: 400 hurdles silver, European Championship 2012: 400m hurdles gold, European Championships

A Team Wales statement added: "The athlete has the opportunity to respond to the charges against him and to have those charges determined at a full hearing before the National Anti-Doping Panel."

Matt Newman, chief executive of Welsh Athletics, said the B-sample was tested on Thursday and matched the A-sample results.

"We shall have the opportunity to go in front of an anti-doping panel, but that's not likely to happen until the autumn," he said.

"In the interim period, it's really now for Rhys to gather together as much information as possible to make a case for the defence."

Williams celebrates becoming European champion in 2012

Williams is the second Welsh athlete to miss the Games over alleged drug violations after 800m runner Gareth Warburton's suspension.

BBC Sport understands the manufacturers of 'Mountain Fuel', a sport supplement used by Williams, are co-operating with the athlete to see whether any of their products are responsible for his failed drugs test.

The company is also believed to be undertaking its own internal tests to establish whether any banned substances were inadvertently used when making the product.

'Mountain Fuel' is thought to be just one of a range of products used by Williams that are being examined.

The results of the tests are expected next Wednesday, with sources close to the company claiming it is confident of being exonerated.

Williams said: "I am utterly devastated about the news of this anti-doping rule violation, which has come as a great shock to me.

"From the outset, I would strongly like to state that I have not knowingly taken any banned substance.

Matt Newman, chief executive of Welsh Athletics, is to launch his own investigation

"However, I recognise that the responsibility for this situation lies with me and I'm committed to working with UK Anti-Doping and will fully cooperate in the legal process."

The suspension is a further blow to Welsh medal hopes, which have also been hit by injuries to key competitors including triathletes Non Stanford and Helen Jenkins and cyclist Becky James.

Team Wales also lost Olympic silver medal-winning boxer Fred Evans, whose accreditation was refused because of his conviction for assault in a nightclub in April.

Reacting to the news, Baroness Grey-Thompson said: "I think withdrawing him is the only thing you can do at this stage.

"I don't think we ever would have expected anything like this from him. It is a huge blow for Wales and for athletics. It's a real shock right now."

Former 1500m world champion Steve Cram added: "It's devastating news for Rhys Williams, for Welsh athletics, for British athletics."

He said athletes have ultimate responsibility for what they put in their bodies, adding: "We can have all sorts of sympathy, but they are just going to have to go with whatever punishment comes their way."