One US service member is missing and three others have been rescued after a US Navy MH-60S Sea Hawk helicopter made an emergency water landing in the Arabian Sea on Wednesday, according to US Naval Forces Central Command. The helicopter, assigned to the aircraft carrier USS George H.W. Bush, went down at approximately 3:30 a.m. Eastern Time (late morning local time) while conducting operations in the area.

Three of the four crew members were recovered from the sea and are in stable condition aboard the carrier, the Bahrain-based US 5th Fleet said in a statement. US Navy vessels and aircraft are continuing to search for the remaining aircrewman, who has not been publicly identified. The military gave no details on the circumstances that forced the helicopter to ditch.

There is no indication that the emergency landing was caused by hostile action, the Navy said, adding that the cause of the incident is under investigation. The statement came as US forces in the Middle East remain on high alert, with security analysts in the Gulf noting that a ceasefire between Washington and Tehran has been punctuated by sporadic flare-ups. The USS George H.W. Bush has been operating in the region since late April, one of two American carriers deployed there.

Helicopter water landings are inherently dangerous, even for experienced pilots, because the aircraft’s top-heavy design can cause it to flip upside down upon submersion, military analysts note. The search for the missing crewman was ongoing as of Wednesday, and no further updates were immediately available.