Four people remain missing in Nepal after the nation’s deadliest plane crash in 30 years, the search is still underway. The black boxes have been recovered, and investigation into the incident proceeded.

A total of 68 bodies have been recovered from the 72 onboard the ATR 72 operated by Yeti Airlines that crashed on Sunday in clear weather in Pokhara.

A scheduled flight from Kathmandu to Pokhara, gateway to the scenic Annapurna mountain range, was carrying 57 Nepalis, five Indians, four Russians, two South Koreans, and one each from Argentina, Ireland, Australia, and France.

Pokhara police official Ajay K.C. said that the search-and-rescue operation, which was suspended because of darkness on Sunday, has resumed and the other 63 bodies had been sent to a hospital. After identification and examination, bodies will be handed over to families.

The passenger flight’s cockpit voice recorder and flight data recorder were found on Monday. Data from the recorders may help investigators determine what caused the ATR 72 to crash.

Teknath Sitaula, a Kathmandu Airport official, said the so-called black boxes are in a good condition judging from outward appearance.

The government of Nepal has declared Monday a day of national mourning and created a panel to investigate the disaster and suggest ways to prevent similar incidents in the future. India’s aviation regulator said it would take all measures to ensure safe aviation in the country’s airspace.

As many as 350 people have died in plane or helicopter crashes in Nepal since 2000, where sudden weather changes can make conditions hazardous. According to experts, it can take months or longer for investigators to determine the cause of air accidents.