Two of the passengers were from a nonprofit that provides aid to Mexican children with severe burns, including transports to a Galveston hospital.

Authorities and volunteers respond to a Mexican Navy plane crash near Galveston, Texas, on Monday.Sky Decker Jr. / via AP

A small Mexican Navy plane transporting a young medical patient and seven others crashed Monday near Galveston, killing at least five people and setting off a search in waters along the Texas coast, officials said.

Four of the people aboard were Navy officers and four were civilians, including a child, Mexico`s Navy said in a statement to The Associated Press. Two of the passengers were from a nonprofit that provides aid to Mexican children with severe burns, including transports to a Galveston hospital.

U.S. Coast Guard Petty Officer Luke Baker said at least five aboard had died but did not identify which passengers.

The cause of the crash is under investigation.

Mexico`s Marines said in a statement that it is sending "its deepest condolences to the families of those who lost their lives in this tragic accident."

The crash took place Monday afternoon in Galveston Bay near the base of the causeway that connects Galveston Island to the mainland. Emergency responders and search teams rushed to the scene near the popular beach destination along the Texas coast that is about 50 miles southeast of Houston.

Sky Decker, a professional yacht captain who lives about a mile from the crash site, said he jumped in his boat to see if he could help. He said he picked up two police officers who directed him through thick fog to a nearly completely submerged plane. Decker jumped in the water and found a badly injured woman trapped beneath chairs and other debris.

"I couldn`t believe. She had maybe 3 inches of air gap to breathe in," he said. "And there was jet fuel in there mixed with the water, fumes real bad. She was really fighting for her life."

He said he also pulled out a man sitting in front of her who had already died. He described both of them as dressed in civilian clothes.

Mexico`s Navy said the plane was helping with a medical mission in coordination with the Michou and Mau Foundation, which provides emergency transports to children with life-threatening burns to Shriners Children`s hospital in Galveston, according to the nonprofit`s website.

The foundation said in a post on social media, "We express our deepest solidarity with the families in light of these events. We share their grief with respect and compassion, honoring their memory and reaffirming our commitment to providing humane, sensitive, and dignified care to children with burns."

The statement from Mexico`s Navy said the plane had an "accident" during its approach to Galveston but did not elaborate.

Teams from the Federal Aviation Administration and National Transportation Safety Board have arrived at the scene of the crash, the Texas Department of Public Safety said on the social platform X.

A spokesperson from NTSB said they are "aware of this accident and are gathering information about it." The Galveston County Sheriff`s Office said officials from its dive team, crime scene unit, drone unit and patrol were responding to the crash.

It`s not immediately clear if weather was a factor. The area has been experiencing foggy conditions over the past few days, according to Cameron Batiste, a National Weather Service meteorologist. He said that at about 2:30 p.m. Monday a fog came in that had about a half-mile visibility.