Saudi Aramco is aiming to restore by Monday about a third of its crude output that was disrupted after drone attacks on two key oil facilities, The Wall Street Journal reported Sunday, citing Saudi officials familiar with the matter.

The drone strikes on facilities in Abqaiq and Khurais eliminated 5.7 million barrels of production over the weekend. Officials believe that they can restore 2 million barrels by the end of the day Monday, contrary to earlier claims that full production would resume early this week.

Aramco, the national oil company, has determined that its facilities were hit by missiles, people familiar with the matter told The Wall Street Journal. A U.S. government assessment determined that up to 15 structures at Abqaiq were damaged.