By Jonathan Saul, Marwa Rashad and Mohamed EzzLONDON/CAIRO, July 29 (Reuters) - A drone caused the fire that engulfed two gas vessels at Egypt's Mediterranean port of Damietta, the Egyptian cabinet said on Thursday, confirming for the first time that the blaze which erupted a day earlier was the result of an attack rather than an accident.No party has claimed responsibility, and authorities were continuing their investigations and taking necessary measures to protect Egypt's national security, the cabinet added.British maritime security firm Ambrey said on Wednesday that a drone had hit a U.S.-owned gas storage tanker at the port, in an initial assessment that raised concerns about a further spread of conflict across the Middle East. Three trading sources familiar with the incident said the drone hit floating storage tanker Energos Winter, causing a fire that spread to another vessel, Gaslog Salem. The Energos Winter was reportedly struck by an unidentified projectile on its starboard side, causing a fire that was extinguished, British maritime risk management group Vanguard said.It was unclear who was responsible for the incident, which occurred shortly after Iran carried out a missile attack against U.S. forces in Jordan, and Washington and Saudi Arabia struck Iran-backed paramilitary groups in Iraq.U.S. President Donald Trump threatened to retaliate against Iran and Yemen's Houthi group declared a naval blockade on Saudi Arabia, apparently spreading the conflict to its widest since the U.S. and Israel started bombing Iran in February.Through a video posted on social media, Reuters was able to verify the location by the port infrastructure, the storage tanks and ship tracking data that matched the archive and satellite imagery.The Energos Winter is a floating storage and regasification unit (FSRU) with storage capacity of 138,250 cubic metres. It is owned by U.S.-based firm Energos Infrastructure. Its technical, safety and commercial operations are managed by Wilhelmsen Ship Management,a Singapore-based subsidiary of Norwegian company Wilhelmsen Group.Egypt's petroleum ministry said in a statement on Wednesday that the fires at Damietta port were dealt with immediately by firefighting and security teams and caused no injuries or fatalities. Petroleum Minister Karim Badawi went to the site to oversee response efforts, it said. (Reporting by Jonathan Saul, Marwa Rashad and Mohamed Ezz; Additional reporting by Nathan Chiang, Monica Naime, Nora Buli, and Tala Ramadan; Editing by Alex Richardson, David Gregorio and Ros Russell)