Iranian media has said a US ScanEagle drone was captured "in the last few days" by the naval unit of the Islamic Revolutionary Guards Corps after entering Iranian airspace while gathering information over Gulf waters.
A US Navy spokesman said they were aware of the reports, and were looking into them.
Last month the US said Iranian warplanes shot at an American surveillance drone flying in international airspace. Iran said the aircraft had entered its airspace.
More top news
Thundery overnight with a Met Office warning for rain in place for a large swathe of the country. Quite sunny throughout tomorrow.
Video shot in Islamic State capital Raqq purportedly shows at least two of three missing London schoolgirls.
A lawyer representing 35 families who lost loved-ones when a pilot deliberately crashed his plane 'can't explain' €25,000 offer.