In Isfahan, where nearly 60% of Iran’s stockpile of already-enriched nuclear material is believed to be stored underground, according to a US official, a US submarine hit the site with Tomahawk cruise missiles, Chairman of the Joint Chiefs Gen. Dan Caine said Sunday.

But unlike the other two Iranian facilities targeted in the operation, B-2 bombers did not drop massive “bunker-buster” bombs on the Isfahan facility, multiple sources told CNN. The damage to the facility appears to be restricted to aboveground structures.

“This is an incomplete strike,” Lewis said. “If this is all there is, here’s what left: the entire stockpile of 60% uranium, which was stored at Isfahan in tunnels that are untouched.”