Diesel additive ( Eolys ) in AdBlue tank

Citroen C3 1.6HDi. The customer come to us with engine and UREA light on. The car was in another garage for a repair and they put wrong fluid in to the AdBlue tank in result of damage pump.  
The vehicle, obviously half the tank for diesel additive (Eolys) but is the separate tank for that.
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