A search is actively underway for a Florida couple and their two grandchildren who are missing after their small private plane crashed into the ocean on Monday while en route from the Bahamas to Florida.

Bahamian authorities received a report that a five-seater PA-34 Piper aircraft, which had departed from Great Harbor Cay, plummeted into the water approximately 13 miles west of Andros Island at 2:20 p.m. local time. The Royal Bahamas Police Force confirmed the incident.

The missing passengers have been identified as pilot Mario Lamar, 80, his wife Lili Lamar, 79, and their grandchildren, 28-year-old Sofia Sosa and 22-year-old Christian Sosa. The family had been vacationing at their second home in Great Harbor Cay and were on their way back to Florida.

According to FlightAware data, the aircraft experienced a rapid fluctuation in speed and a sudden drop in altitude from 10,000 feet to 3,700 feet within a three-minute span before disappearing from radar. The flight had encountered rough weather near the north end of Andros Island, which initially hampered search efforts.

The U.S. Coast Guard is assisting Bahamian authorities in the search operation with an HC-144 Ocean Sentry airplane. A niece of Mario and Lili Lamar issued a public plea for help with the search and rescue efforts.

Mario Lamar, the pilot, was described by his family as well-trained with over 40 years of flying experience. Sofia Sosa is a recent graduate of Wake Forest University, and Christian Sosa recently graduated from Loyola Marymount University.