© AP Photo/Indonesia Air Force's Elite ForceThe wreckage of a Spanish-designed aircraft CASA C-212 is seen in Bahorok, North Sumatra, Friday, Sept. 30, 2011.
The bodies of all 18 people who were on board a plane that crashed into the jungle-covered mountains of western Indonesia were recovered from the wreckage Saturday, an official said.

The Spanish-designed CASA C-212 lost contact with air traffic control early Thursday while flying from North Sumatra to Aceh province. Minutes later, it sent out a distress signal, then dropped off the radar.

Rugged, forested terrain and bad weather had prevented rescuers from reaching the crash site by foot, and the wreckage was spotted from a helicopter Friday in the Leuser mountains at an altitude of 5,000 feet (1,524 meters).

Early Saturday, 13 rescuers were lowered by helicopter by rope to the crash site, following two others who had reached the site just before darkness fell Friday.

"They found the bodies in their seats with their seat belts on," Sunarbowo Sandi, head of the local search-and-rescue team, told The Associated Press from his monitoring post in a village near the crash site in the Bahorok region, about 930 miles (1,500 kilometers) northwest of the capital, Jakarta.

The bodies included all 14 passengers and four crew members. Four of the dead were children.

Hopes had been raised that there may be survivors after the aircraft was spotted intact with one of its doors open, and rescuers dropped food and medicine down to the crash site.

The victims' relatives, who had been waiting for information, broke down in tears when they learned that their loved ones were found dead. Many of them accused the airline - PT Nusantara Buana Air - of taking far too long to give them information.

"The rescue operation was too slow and unprofessional," Rosmawati Harahap, who lost her son, daughter-in-law and two grandchildren in the crash, said while sobbing.

But rescuers insisted that tornado-like winds and heavy fog hampered their efforts to reach the crash site.

"The conditions were really bad," said Sandi, the search-and-rescue official, adding that rescuers were further hampered by the mountainous terrain and impenetrable forests.

Robur Rizallianto, a safety manager with the airline, said "all efforts" were made to try to save the passengers.

It was unclear what caused the crash, and Indonesia's transportation safety commission was investigating the accident.

The aircraft, made in Indonesia in 1989, was last inspected Sept. 22, according to Rizallianto. It was in good condition, and a check ahead of takeoff Thursday also came up clean, he said.

Indonesia, a sprawling archipelagic nation of 240 million people, has been plagued by transportation accidents in recent years, from plane and train crashes to ferry sinkings. Many are blamed on overcrowding and poor safety standards.