ISLAMABAD (AP) — A cargo plane with five crew members aboard went missing off the Pakistani port of Karachi late Tuesday after rapidly descending and losing contact with air traffic controllers on a flight from United Arab Emirates, officials said.

Pakistan’s airport authority posted on X that search and rescue operations were underway in the Arabian Sea. The cause of the aircraft’s disappearance was not immediately known.

The Boeing 737 was being operated by Karachi-based K2 Airways on a cargo flight from Sharjah in the UAE to Karachi when it reported a navigation system problem at 9:18 p.m. local time, the authority said.

Radar data showed the aircraft rapidly descending and making a sharp change in heading at about 9:21 p.m. before radar and radio contact were lost about 155 nautical miles (287 kilometers, 178 miles) west of Karachi, the authority said.

Authorities responded by activating the Rescue Coordination Center and search and rescue operations were launched at sea through various agencies to locate the missing aircraft, according to the airport authority.

Aviation expert Imran Aslam told local ARY News that it remains unclear what caused the aircraft to disappear from radar. He said that even if an aircraft suffers an engine failure, it would normally continue gliding rather than plunge suddenly. “I still cannot understand how the plane went down so abruptly instead of gliding,” he said.

According to the K2 Airways website, it is a private cargo airline based in Karachi and was established in May 2018.

Authorities said Pakistan’s military and civilian authorities had deployed multiple air and sea assets for the search and rescue operation. According to multiple officials, the Pakistan Navy frigate PNS Zulfiqar was quickly diverted to the area where contact with the aircraft was lost. They said the Pakistan Air Force had also deployed aircraft for the effort, while a Pakistan Navy ATR aircraft took off from Turbat to assist in the operation.

The officials said the Pakistan National Shipping Corp. merchant vessel had also been dispatched and was participating in the search.

In May 2020 a Pakistani jetliner carrying 98 people crashed in a crowded neighborhood near the airport in Karachi, the capital of Sindh province, after an apparent engine failure during landing. All but one passenger died in the crash. Later, Pakistan’s government released a report saying human error on the part of the pilot, the co-pilot and air traffic control caused the Pakistan International Airlines crash.