The warehouse, which Iran said was a carpet-cleaning facility, is on the outskirts of Tehran in a village called Turquz Abad. Commercial satellite photography purchased by the Washington-based, nonpartisan Institute for Science and International Security shows the site being gradually emptied of multiple large containers between July and September of 2018, following Israel’s heist earlier that year of a huge cache of Iranian nuclear documents.

As for the I.A.E.A., the agency only got around to inspecting the site earlier this year, long after the suspicious materials had vanished, and Amano died in July. But nuclear inspectors were nonetheless able to detect radioactive particles, corroborating Israeli claims about the purpose of the warehouse. On Monday, The Wall Street Journal reported that Iran is now refusing to answer the agency’s questions about just what material was stored at the warehouse — and, more importantly, where it might be now.

So what’s new?

Some defenders of the 2015 nuclear deal are prone to answer: Not a lot. Traces of radioactive material may be the residue of Iran’s old nuclear-weapons program, which is generally thought to have been shuttered around 2003. Tehran has always been notoriously recalcitrant when it comes to responding to the I.A.E.A. And after the Iraq W.M.D. debacle, it’s wise to avoid drawing stark conclusions from incomplete and possibly false nuclear evidence.

Then again, the history of nuclear inspections has more false negatives than it does false positives, including the agency’s past failures to find Iran’s secret nuclear facilities in Natanz and Arak. Its unwillingness to follow up promptly and effectively on Israel’s allegations about Turquz Abad, along with its reluctance to disclose what it found, inspire little confidence in the quality of its inspections and even less in its willingness to call out cheating.

As for Iran, hiding nuclear materials is a violation of its basic reporting obligations to the I.A.E.A. It’s also further evidence that Tehran was in violation of the nuclear deal from the moment it was signed. “If Iranians aren’t cooperating, it tells you that potentially they are hiding more,” notes the Institute for Science and International Security president, David Albright, adding that the Turquz Abad findings are “a big deal.”