(CNN) Double Olympic gold medalist Mo Farah -- under investigation by UK Athletics following a recent BBC documentary which raised questions over the methods of his coach Alberto Salazar -- has released a statement on his Facebook account saying he has never doped.

In the run-up to the 2012 Olympics Farah began working with Cuban-American Salazar at his Portland, Oregon training facility but missed two doping tests leading up to the London Games.

UK Anti-Doping rules stated that an athlete who missed three tests in any 18-month period could face a ban of up to two years.

One slip-up occurred in early 2010, before he teamed up with Salazar, while the other took place a year later when Farah claimed to have not heard his doorbell.

"I have never taken performance enhancing drugs in my life and I never will," said Farah on Facebook.

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