A senior U.S. official is dismissing a report that says covert American drone strikes in Pakistan have killed 385 civilians, nearly half of them children, saying the findings by the London-based Bureau for Investigative Journalism are faulty and uncorroborated. The response by the official late Thursday follows a report released this week by the nonprofit group, which includes British and Pakistani journalists, that found drone strikes since 2004 killed at least 2,292 people. Of those killed in the strikes, the group said it had credible reports of at least 385 civilians, including 160 children. "The numbers cited by this organization are way off the mark," the official told CNN. The official spoke on condition of anonymity because of the sensitivity of the drone program. According to the senior U.S. official, an estimated 2,000 militants and 50 civilians have been killed in strikes since 2001. Since May 2010, the strikes have killed 600 militants, the official said. "In that same period of time, we can''t confirm any noncombatant casualties," the official said. The Bureau of Investigative Journalism defended its report in a statement to CNN on Friday, calling it "the most accurate public record yet of the CIA''s drone strikes.