Mamadou Sakho
Sakho's currently under Uefa investigation.Getty

Liverpool manager Jurgen Klopp says there is nothing else the club can do regarding Mamadou Sakho's ongoing drug test controversy.

Sakho, 26, is being investigated over a possible anti-doping violation and has been made unavailable for selection by his club. He is not currently subject to any official Uefa suspension, however.

BBC Sport claimed the France international has decided not to challenge a failed drugs test, thought to be for a type of fat burner.

Speaking ahead of Liverpool's Europa League semi-final clash with Villarreal, Klopp was unable to provide any further update as the investigation continues.

"There is nothing else we can say," he told a press conference. "I think what they are all doing is collecting all the information to clear the situation as much as possible. We have to wait for the next step, it is not as if we can force anything, we have to wait. We did what we thought was right, that is all, there is nothing else to say."

The test in question took place following Liverpool's quarter-final second leg draw against Manchester United at Old Trafford.

Liverpool are in action at the Estadio El Madrigal on 28 April with Christian Benteke in line to make his first appearance since the 3-2 defeat to Southampton on 23 March.

The Belgium international travelled with the Liverpool squad to Spain and Klopp says no one was included merely to make up the numbers.

"It is great he is back. He has not had many sessions in last few weeks but last few days he came back. We were watching him in training. He is in the best shape, after injury it wasn't easy [for him] now it is better."

"It is perfect he is back. We only have players here that will play a part tomorrow. No tourists."