Boeing Shares fell nearly 5% in premarket trading on Monday after South Korea ordered an inspection of all B737-800 planes, the model involved in a fatal Jeju Air crash over the weekend.

Acting President Choi Sang-mok called on the Transportation Ministry to conduct an emergency safety inspection of the country’s entire air operations system, while officials at the Ministry of Land, Infrastructure and Transport (MOLIT) said they would conduct a “comprehensive special inspection” of the B737-800 .”

New York-listed Boeing shares fell 4.7% in premarket trading before paring losses to trade 4% lower as of 6:10 a.m. ET.

The exact circumstances of the crash, which killed 179 of 181 people, are uncertain on board the flight on Sunday. The plane landed at South Korea’s Muan International Airport without proper equipment, skidded off the runway and crashed into an outside wall before bursting into flames. The survivors were two crew members who were rescued from the rubble.

In a briefing on Monday, MOLIT said the plane’s pilot mentioned a “bird strike” minutes after the airport’s control tower issued a bird activity alert. The pilot also notified the control tower of a “go-around,” indicating an aborted landing attempt, and declared “mayday,” said Yu Kyung-soo, director of aviation safety policy at MOLIT, according to an NBC News translation.

Two black boxes were recovered from the aircraft and sent for analysis. The U.S. National Transportation Safety Board is now leading a team of American investigators, including the Federal Aviation Administration and Boeing, to help South Korea’s Aviation and Railway Accident Investigation Board investigate the crash.

MOLIT officials said Monday they were examining the concrete wall the plane crashed into for a link to the accident.

They also said they would conduct a “comprehensive special inspection of the B737-800 model.”

Boeing’s popular narrow-body aircraft has been in service for nearly three decades, with development predating the US manufacturer’s troubled B737 Max jets, a later version of the model.

The B737-800 is widely used by South Korean budget airlines, MOLIT said on Monday, with Jeju Air being the largest operator with 39 jets. Other operators include T’way Air, Jin Air, Eastar Jet and Air Incheon, while Korean Air operates two of these models.

“We will check compliance with various regulations, including operational records, inspections and maintenance before and after flights,” Ju Jong-wan, director of the Aviation Policy Office at MOLIT, said on Monday, according to NBC News translation.

“We plan to review stricter regulations regarding bird strikes, which have been identified as a potential cause of accidents, particularly for new airports under construction.”

CNBC has reached out to Boeing for comment.

Local media reported that another Jeju Air plane of the same model returned to South Korea’s Gimpo Airport shortly after takeoff on Monday after reporting problems with its landing gear.

At a news conference on Sunday, Song Kyung-hoon, head of Jeju Air’s management support office, said the airline would support the victims and their families and that the plane would be covered by $1 billion in insurance, according to the Yonhap news site. dollar is hedged.

Song also denied that mechanical failures or inadequate safety precautions played a role in the crash.

“This crash is not about maintenance issues. There can be absolutely no compromise when it comes to aircraft maintenance,” Song said.

Jeju Air shares hit an all-time low on Monday, closing 8.65% lower, according to FactSet data.

— CNBC’s Yeo Boon Ping contributed to this story.