SEOUL, South Korea — A team of U.S. investigators including representatives from Boeing on Tuesday examined the site of a plane crash that killed 179 people in South Korea while authorities were conducting safety inspections on all Boeing 737-800 aircraft operated by the country’s airlines.

All but two of the 181 people aboard the Boeing 737-800 operated by South Korean budget airline Jeju Air died in Sunday’s crash. Video showed that the aircraft, without its landing gear deployed, crash-landed on its belly and overshot a runaway at South Korea’s southern Muan International Airport before it slammed into a concrete fence and burst into a flame.

The plane was seen having engine trouble, and preliminary examinations also say the pilots received a bird strike warning from the ground control center and issued a distress signal. But many experts say the landing gear issue was likely the main cause of the crash.

The South Korean government has launched safety inspections on all the 101 Boeing 737-800s in the country. The Transport Ministry said authorities are looking at maintenance and operation records during five days of safety checks that are to run until Friday.

The ministry said that a delegation of eight U.S. investigators — one from the Federal Aviation Administration, three from the National Transportation Safety Board and four from Boeing — made an on-site visit to the crash site Tuesday.

The results of their examination weren’t available.

Kim E-bae, Jeju Air’s president, told reporters Tuesday that his company will add more maintenance workers and reduce flight operations by 10-15% until March as part of efforts to enhance the safety of aircraft operations.

The Boeing 737-800, an earlier version of 737 than the Max, is a widely used plane with a good safety record, said Najmedin Meshkati, an engineering professor at the University of Southern California.

He said the failure of the plane’s system for broadcasting location, operating its landing gear and extending the wing flaps to slow down indicate a widespread problem that affected electrical and hydraulic systems. Meshkati said he is confident that investigators will learn what went wrong by analyzing information from the flight data and cockpit voice recorders.

The crash was the deadliest disaster in South Korea’s aviation history in decades. A national mourning has been declared until Saturday.

The Transport Ministry said authorities have identified 175 bodies and are conducting DNA tests to identify the remaining four. Bereaved families said thatofficials told them that the bodies were so badly damaged that officials need time before returning them to relatives.