PANGKALAN BUN, Indonesia (AP) — After nearly a week of searching for the victims of AirAsia Flight 8501, rescue teams battling monsoon rains had their most successful day yet on Friday, more than tripling the number of bodies pulled from the Java Sea so far. An Indonesian navy official said some of the dead were still strapped to their seats.

Of the 30 corpses recovered in total, 21 were found on Friday, many of them by a U.S. Navy ship, according to officials.

The Airbus A320 carrying 162 passengers and crew went down Sunday, halfway into a flight from Surabaya, Indonesia's second-largest city, to Singapore. Minutes before losing contact, the pilot told air-traffic control he was approaching threatening clouds, but was denied permission to climb to a higher altitude because of heavy air traffic.

It remains unclear what caused it to plunge into the sea.

Col. Yayan Sofiyan, commander of the warship Bung Tomo, told MetroTV five bodies pulled in by his crew were still fastened in their seats.

Indonesian search and rescue chief Henry Bambang Soelistyo said he knew of only two victims found in their seats, but said a total of 30 bodies have been recovered.

Rescue teams hope many of those on board are still within the fuselage, which has not been located.

Several countries involved in the massive effort are using sophisticated sonar equipment and metal detectors to scour the relatively shallow ocean floor for the wreckage — and the plane's black boxes.

"We will focus on underwater detection," said Indonesia's Search and Rescue Agency chief Henry Bambang Soelistyo.