An explosion is believed to have damaged Iran’s Fordow nuclear facility, which is being used to enrich uranium, Israeli intelligence officials have told The Times. Sources in Tel Aviv said yesterday that they thought the explosion happened last week. The Israeli Government is investigating reports that it led to extensive structural damage and 200 workers had been trapped inside.

Israel believes the Iranians have not evacuated the surrounding area. It is unclear whether that is because no harmful substances have been released, or because Tehran is trying to avoid sparking panic among residents.

The Fordow plant is buried deep underground inside a mountain near the holy city of Qom. It is thought to be Iran’s most heavily fortified facility and is regarded as impervious to