A joint investigation by the Washington Post and PBS Frontline found increased construction activity at Pickaxe Mountain, a deep underground site near Iran's Natanz nuclear facility, following U.S. and Israeli strikes on Iran's nuclear infrastructure in June. Two tunnel entrances had been fortified and there was evidence of continuing tunneling activity. Ali Larijani, secretary of Iran's Supreme National Security Council, confirmed that Iran was still using the site. Iranian officials have said that Pickaxe Mountain is intended for centrifuge manufacturing, though analysts say the site could be used for uranium enrichment or storage of enriched uranium.