Night-vision equipment believed to be British has been discovered in Hezbollah command bunkers in southern Lebanon, Israeli forces have said.
Israeli soldiers are said to have found the equipment
The Foreign Office is trying to ascertain the kit manufacturer and how it may have ended up in militant hands.
It is thought that the equipment was not among a batch sold to Iran in 2003 under a special export licence for use against drug smugglers.
The government only permits supply of such equipment for non-military use.
The Times said checks were being made to compare serial numbers on the equipment found by the Israelis with the ones legitimately exported to Iran.
"The Israeli Defence Forces have confirmed to us that they have found some night vision equipment, which they believe to be British, in southern Lebanon," a Foreign Office spokesman said.
"We are seeking further details of the equipment to investigate whether it is British and, if so, by whom it was made and to whom it was sold."
The deployment of a UN force and Lebanese government troops to the south of the country, where Hezbollah have been active, is one of the conditions of a ceasefire.
The UN wants 3,500 troops on the ground by the end of August, to be increased later to 15,000.