By Fergus Jensen and Fransiska Nangoy

PANGKALAN BUN/SURABAYA, Indonesia (Reuters) - Bad weather forced divers trying to identify sunken wreckage from a crashed AirAsia passenger jet to abort their mission on Sunday and Indonesian officials said they had not yet picked up any signals from the lost plane's "black box".

Indonesia's meteorological agency has said seasonal tropical storms probably contributed to last Sunday's crash and the weather has persistently hampered efforts to recover bodies and find the cockpit voice and flight data recorders that may explain why the Airbus A320-200 plunged into the sea.

"Conditions did not allow diving operations," the head of Indonesia's search and rescue agency, Fransiskus Bambang Soelistyo, told a news conference in Jakarta. "Our priority is to dive in the location we suspect parts of the plane to be."

Flight QZ8501 crashed into the Java Sea about 40 minutes after taking off last Sunday from Indonesia's second-largest city Surabaya en route for Singapore. There were no survivors.

The main focus of the search is about 90 nautical miles off the coast of Borneo island, where five large objects believed to be parts of the plane -- the largest about 18 meters (59 feet) long -- have been pinpointed by ships using sonar.

"Based on past experience, the black box is not far from the plane debris we have found," Soelistyo said. But he added that none of the searching ships had detected any "pings", the locator signals the black box should transmit after a crash.

Until investigators can examine the black box recorders the cause of the crash remains a mystery, but the area is known for intense seasonal storms. BMKG, Indonesia's meteorological agency, has said bad weather may have caused ice to form on the aircraft's engines.

"The flight document provided by the BMKG office shows fairly worrying weather conditions for the aircraft at cruising level on the chosen route," the agency said in a report.

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BAD WEATHER

Both flight recorders are located near the tail of the Airbus, but it was unclear whether that part of the aircraft was among the debris found on the seabed.

"Based on the finding of pieces of debris it looks like the body of the aircraft split or cracked and was separated from its tail," said Air Force Lt Col Johnson Supriyadi, a search and rescue official co-ordinating the operation from the southern Borneo town of Pangkalan Bun.

The suspected wreckage is lying in water around 30 meters deep, which experts say should make it relatively straightforward to recover.

Nine ships from four countries have converged on the area, with teams of divers including seven Russian experts standing ready, but strong winds and four-meter high waves have kept progress agonizingly slow.

"There's a storm ... Earlier, four divers were transferred to (Indonesian navy ship) KRI Banda Aceh but they canceled the diving because the sea currents were too strong," said a Reuters photographer on board one vessel.

Second Sergeant Akhyar of the search and rescue agency described what it was like being winched onto the deck of a ship to collect bodies in such conditions.

"The wind makes you spin and I'm quite light, so I get blown left and right, swinging," he said.

BODIES MAY BE IN FUSELAGE

Thirty-four bodies of the mostly Indonesian passengers and crew have so far been recovered, including some still strapped in their seats. Many more may be still trapped in the fuselage of the aircraft.

"This big part of the plane, we still have hope that victims are still inside the body of the plane," said Soelistiyo, adding that he was referring to one of the five objects found.

The crash was the first fatal accident suffered by the AirAsia budget group, whose Indonesian affiliate flies from at least 15 destinations across the sprawling archipelago.

The airline has come under pressure from Indonesian authorities, who have suspended its Surabaya to Singapore operations saying the carrier only had a license to fly the route on Mondays, Tuesdays, Thursdays and Saturdays.

Indonesia AirAsia said it would co-operate with the transport ministry while it investigates the license.

A joint statement from Singapore's civil aviation authority (CAAS) and Changi Airport Group said that AirAsia had the necessary approvals to operate a daily flight between Surabaya and Singapore.

(Additional reporting by Beawiharta ABOARD KN PURWOREJO, Nilufar Rizki, Adriana Nina Kusuma, Chris Nusatya, Cindy Silviana, Kanupriya Kapoor, Michael Taylor, Charlotte Greenfield and Nicholas Owen in JAKARTA, and Anshuman Daga in SINGAPORE; Writing by Alex Richardson; Editing by Michael Perry, Kim Coghill and Gareth Jones)