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Chelsea saw an offer in excess of €20 million for the Germany international previously turned down, with the Bundesliga side unwilling to lose a player of such importance to a European rival.
The Champions League winners are now believed to be preparing an improved offer for the 21-year-old, but Leverkusen have insisted the attacker is not for sale at any price.
"There is simply no asking price in this case as there is no alternative solution," Holzhauser told Bild.
"We have already said everything there's to say on this matter. Andre is an important player for Leverkusen."
Schurrle joined Leverkusen from Mainz in the summer of 2011 and has gone onto become a key player at the BayArena and also for the German national team.
His contract with Leverkusen is due to expire in June 2016.