BlackRock and MSC’s attempt to acquire most of CK Hutchison’s global port operations has hit a regulatory hurdle in Europe, with EU antitrust officials preparing to investigate the Spanish portion of the transaction, a person with direct knowledge of the matter said on Thursday.

CK Hutchison, controlled by Hong Kong tycoon Li Ka-shing, is seeking to sell its 80% stake in the $22.8 billion ports business, which spans 43 ports across 23 countries. The politically sensitive deal has drawn heightened attention amid ongoing China–U.S. tensions.