Activision has officially responded to G4 about the reported shakeup at Infinity Ward. The publisher has confirmed that studio heads Vince Zampella and Jason West have left the company, but issued no other comment related to their departure. Activision Publishing CTO Steve Pearce and head of production Steve Ackrich are temporarily in charge of Infinity Ward.

According to Activision, Infinity Ward will move forward on developing two downloadable map packs for Call of Duty: Modern Warfare 2, for release later this year. A new Call of Duty is also coming from Treyarch Games in 2010, and Sledgehammer Games will release a brand-new Call of Duty game “in the action-adventure genre” next year.