Media playback is unsupported on your device Media caption Rupert Wingfield-Hayes: Search teams want divers to make visual identification

Search teams scanning the Java Sea for the main wreckage from AirAsia flight QZ8501 have found "four large objects", the search chief says.

Bambang Soelistyo said the biggest of the objects was 18m (59ft) long and he believed they were parts of the plane.

The Airbus A320 vanished with 162 people on board en route from Surabaya in Indonesia to Singapore last Sunday.

So far 30 bodies have been recovered with most of the remaining bodies thought to be trapped in the fuselage.

Indonesia's weather agency believes bad weather was the "biggest factor" behind the crash, in which no survivors were found.

The BBC's Rupert Wingfield-Hayes at the forward operating base in Pangkalan Bun says it seems this could be the breakthrough search teams have been hoping for.

The cause of the crash is not yet known. Specialist equipment has arrived to the search for the plane's "black-box" flight recorders, though officials say no signals have been picked up yet.

'Confident'

Sonar from an Indonesian navy ship detected one large object on Friday night with the other three found on Saturday, Mr Soelistyo announced.

"I am confident these are parts of the missing AirAsia plane," he said.

According to the Associated Press news agency, he also gave the width of the largest object found, saying it was 5.4m. Another was said to be 10m long.

Mr Soelistyo said an ROV (remotely operated underwater vehicle) was being lowered into the water to get an actual picture of the objects, which were at a depth of 30m.

He warned that the height of waves was hampering the search effort at sea. The waves were four to five metres high, he said.

Another official, Supriyadi, said earlier that poor visibility was hampering the work of the ROVs.

'Weather a factor'

An initial analysis by Indonesian weather agency BMKG has found that conditions at the time of the plane's disappearance suggest it probably flew into a storm.

Professor Edvin Aldrian, head of research at BMKG, said there was evidence of extremely icy conditions at the plane's altitude, which can "stall the engines of the plane and freeze and damage the plane's machinery".

Officials have said the plane was travelling at 32,000ft when it requested to climb to 38,000ft to avoid bad weather.

Some investigators are reported to believe that the plane may have gone into an aerodynamic stall as the pilot climbed steeply.

Image copyright Getty Images Image caption Bodies of the victims are being taken to Surabaya after being recovered from the sea

In another development, it has emerged that AirAsia did not have official permission to fly the Surabaya-Singapore route on Sunday but was licensed on four other days of the week.

There were 137 adult passengers, 17 children and one infant, along with two pilots and five crew, on the plane - the majority Indonesian.

After bodies are recovered from the sea they are transported in numbered coffins for identification in Surabaya, Indonesia's second largest city.