Sunderland chief Lee Congerton posted scouts to Holland yesterday.
AD says a Sunderland delegation attended FC Utrecht's clash with SC Heerenveen.
The focus of their attention was Utrecht striker Sebastien Haller.
Haller has been an Eredivisie revelation since his January market arrival. Last season, the Frenchman scored 11 goals in 17 games.
And he has already kicked off this term with three goals.
Brentford made enquiries earlier this month for Haller, but were put off by Utrecht's €9 million asking price.