Several media outlets reported on Tuesday that the 22-year-old defender failed a drugs test in November.

A club statement said Diaby was "subject to a playing suspension whilst this matter is under investigation".

The statement added: "The player and club are cooperating and responding directly with the FA."

Diaby joined Barnsley from Belgian club KSC Lokeren for an undisclosed fee last summer, after agreeing a four-year contract.

He did not feature in either of Barnsley's past two Championship matches against Bristol City and Preston, with head coach Gerhard Struber telling BBC Radio Sheffield that the centre-back was suffering with a knee injury.

When asked about the reports that Diaby had failed a drugs test, Struber said: "The process is running, it's not clear.

"I think there will be more information in the next week and now is not the right time to tell more."