Iran has reportedly collapsed tunnel entrances and placed explosive mines around parts of its highly enriched uranium stockpile near Isfahan. CNN reports.

•⁠ ⁠The measures are said to have been taken after President Trump publicly raised the possibility of a U.S. operation to secure Iran’s enriched uranium, which intelligence officials estimate totals roughly half a ton.

•⁠ ⁠U.S. intelligence officials and nuclear experts cited in the report say the new fortifications have made any potential effort to recover or remove the uranium significantly more difficult.