Galveston, Texas - At least five people were killed after a Mexican Navy aircraft crashed in the waters of Galveston Bay in Texas while carrying out a medical transfer, authorities announced Monday.

Eight people were traveling aboard the aircraft, which was on a humanitarian mission, the Mexican Navy Secretariat said in a statement. Among the victims is a two-year-old child.

Two people survived the crash while five others died, according to the agency, increasing the death toll from two as previously reported.

One person on the flight remains missing, despite search efforts by the US Coast Guard, the secretariat added.

The specialized medical transport mission was coordinated with a Mexican foundation that cares for children with severe burns.

Per the tracking website Flight Radar, the plane took off from Merida in Mexico's Yucatan state at 6:46 PM GMT (1:46 PM ET) and was last recorded just after 3 PM CT over Galveston Bay, near Scholes International Airport.

Visibility was reported as poor – around 30 yards, according to a local speaking to KTRK.

One of the survivors was rescued by a man who was out sailing on the bay when the crash occurred. Sky Decker told CNN that he jumped into the water to free a woman trapped in the debris.