At least five people were killed after a small Mexican Navy aircraft on a medical mission crashed into waters near Galveston, Texas, on Monday afternoon, triggering a large-scale search and rescue operation, officials said.

The plane was carrying eight people, including four Mexican Navy officers and four civilians, among them a child, according to Mexico’s Navy. Two of the civilians were linked to a nonprofit organisation that assists Mexican children with severe burns and helps transport them to hospitals in the United States.

U.S. Coast Guard Petty Officer Luke Baker confirmed that at least five people died in the crash, though the identities of the victims were not immediately released. The cause of the crash remains under investigation.

The aircraft went down in Galveston Bay near the base of the causeway connecting Galveston Island to the mainland, about 50 miles southeast of Houston. Emergency responders and search teams rushed to the scene in the busy coastal area.

A local yacht captain, Sky Decker, who joined rescue efforts, said he found a badly injured woman trapped inside the nearly submerged plane amid debris and fuel fumes. He also recovered the body of another passenger, whom he said had already died.

Mexico’s Navy said the plane was supporting a medical mission in coordination with the Michou and Mau Foundation, which provides emergency transport for children with life-threatening burns to Shriners Children’s Hospital in Galveston.

The foundation expressed condolences to the victims’ families and reaffirmed its commitment to helping burn patients. Mexican authorities also conveyed deep sympathy to those affected.

Teams from the US Federal Aviation Administration and the National Transportation Safety Board have arrived to investigate the incident. Officials said weather conditions, including fog that reduced visibility to about half a mile, may have been a factor, though this has not been confirmed.