ROME — A prototype UAV designed by Piaggio Aero has crashed into the Mediterranean Sea during a test flight, the firm has said.

The P.1HH, also known as the Hammerhead, which crashed off Sicily on May 31, was the only version of the UAV currently flying, according to the company.

"A Task Force is flying towards the area to start recovery of the aircraft," the firm said in a statement.

Italy-based Piaggio Aero is controlled by Mubadala, an Abu Dhabi-based strategic investment firm.

In March, the United Arab Emirates signed a €316 million (US $352 million) contract to purchase eight of the UAVs, which are based on Piaggio Aero's manned P180 twin prop business aircraft.

Piaggio Aero previously said the Italian Air Force, which has been closely involved in the development and flight testing of the UAV, would be the launch customer this year.

Given that the crashed aircraft was the only version flying, the delivery schedule may suffer while investigators seek the cause of the incident.