Divers were grappling with light rain and rolling waves Sunday as they tried to reach what is believed to be the fuselage of AirAsia Flight 8501, resting on the ocean floor near three other large objects.

So far, only 30 bodies have been recovered from last week’s crash and officials believe many of the remaining 132 passengers and crew are strapped to their seats inside the plane, said National Search and Rescue deputy chief Tatang Zainudin.

“We are racing with time and weather in running this mission,” he said, as early morning clear skies slowly became overcast.

The plane went down in the Java Sea on Dec. 28, halfway into a two-hour flight from Surabaya, Indonesia’s second-largest city, to Singapore. Minutes before losing contact, the pilot told air traffic control that he was approaching threatening clouds, but was denied permission to climb to a higher altitude because of heavy air traffic.

What caused the disaster remains unclear, but Indonesia’s Meteorology, Climatology and Geophysics Agency released a report, saying “Flight 8501 appears to have been trapped in bad weather that would have been difficult to avoid.”

While the plane’s black boxes ? the flight data and cockpit voice recorders ? have yet to be located, the discovery of the wreckage would greatly benefit the investigation.

Sonar equipment identified four giant chunks on the sea bed in the target search area on Friday and Saturday, but no images have been captured confirming they are part of the AirAsia plane.

The biggest object, measuring 18 meters (59 feet) long and 5.4 meters (18 feet) wide, appeared to be part of the jet’s body, said Henry Bambang Soelistyo, chief of the National Search and Rescue Agency.

Other chunks of debris measured up to 12 meters (39 feet) long. Suspected plane parts also were seen scattered on beaches during an aerial survey.

Generally, aviation experts say the more passengers, luggage and parts of the aircraft that remain intact, the more likely the plane hit the water in one piece. That would signal problems like a mechanical error or a stall instead of a midair breakup due to an explosion or sudden depressurization.

(AP)