Hydrogen race balloonists missing in Adriatic storm
No distress beacon has been picked up from Mr Abruzzo's balloon
Two balloonists taking part in the Gordon Bennett Cup race are missing in thunderstorms over the Adriatic.
The Italian coastguard said boats would continue to search for them through the night but aircraft would have to stop at 1900 BST when it got dark.
The missing hydrogen balloon, piloted by Richard Abruzzo and Carol Rymer Davis, is one of three US entries.
A spokeswoman at race control in Bristol said contact had been lost with the American pilots.
Massimo Maccheroni, of the Italian coastguard, said they last had contact with the pair at 0800 local time (0700 BST).
He said the pilots reported bad weather conditions. He said: "We are searching the sea 13 miles off Cap Gargano in the Puglia area.
"We have three boats, two helicopters and two aircraft involved in the search at present.
"The balloon could also have landed on the ground near Foggia and we have also been advised that it could have possibly landed in Croatia."
One of the British entries, piloted by Wiltshire-based David Hempleman-Adams and Simon Carey, landed in third place.
The balloon landed in eastern Serbia having travelled 1,248 miles (2,009.54km), some 270 miles from the American balloon.
Mr Hempleman-Adams said the weather was starting to change.
"Around the mountains here there was a convection which was taking us up and down 700ft so the whole basket was shaking underneath. It was like being in a very fast lift up and down.
"So this morning it was a bit scary at times.
"It took quite a long time to find a suitable place but Simon did a fantastic landing. A fabulous landing."
Don Cameron, from race control, said the last satellite tracker report from the missing balloon - USA2 - was at 0658 BST.
"The Italian Maritime Rescue Co-ordination Centre have initiated an operation with a helicopter and fast boat although no ELT [distress beacon] activation has been detected so far," he said.
"The Croatian authorities and all shipping have been informed.
"Thunderstorm activity has been reported in the area. We are very concerned, but can only wait for news now."
The spokeswoman from race control in Bristol said organisers were in touch with the missing balloon's ground team and Italian air traffic control.
The balloons took off from a launch site to the north of Bristol on Saturday night.
The winning team is the one to travel the furthest and crew control the balloon by letting gas out to descend or throwing sandbags out to ascend.
At first light on Wednesday just three teams of the 20 that started, including the Americans, were still flying in the Gordon Bennett 2010 international gas balloon race.
By 1140 BST all other competitors had landed.
The Swiss team - SWI2 - made up of Kurt Frieden and Pascal Witpraechtiger, landed near Constanta, Romania, in first place, having travelled 1,513 miles (2,435.08km).
A German balloon piloted by Wilhelm Eimers and Ullrich Seel landed in second place, in Moldova, having travelled 1,438 miles (2,313.40km).