President Donald Trump declared that Iran’s nuclear enrichment facilities were “completely and totally obliterated” following this weekend’s air strikes, but the US appears to have held back its most powerful bombs against one of the three facilities included in the operation, raising questions about whether it finished the job.

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, according to Jeffrey Lewis, a weapons expert and professor at the Middlebury Institute of International Studies who has closely reviewed commercial satellite imagery of the strike sites.

Even if the US was successful in destroying Iran’s facility at Fordow — another underground site that housed centrifuges needed to enrich uranium, which the US hit with 12 bunker busters — the obvious survival of Isfahan has raised questions about whether Trump achieved his stated goal of “a stop to the nuclear threat posed by the world’s No. 1 state sponsor of terror.”

“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.”

A satellite image taken by Airbus shows significant damage to the Isfahan site and signs that the underground portion of the facility was hit, according to the Institute for Science and International Security, which analyzed the image. But there are layers of tunnels at the facility, so it’s unclear how far the damage goes.