A 16-year-old US sailor attempting to break Jessica Watson's solo sailing record has gone missing in the Indian Ocean, US media reported Thursday citing her family.

A rescue effort was launched off the coast of Madagascar early Thursday after emergency beacons on board Abby Sunderland's sailboat were triggered after the young adventurer ran into 50-60 foot seas.

Five months younger than Jessica Watson, Sunderland is attempting to break her solo sailing voyage around the world.

Sunderland, from the Los Angeles suburb of Thousand Oaks, was believed to be hundreds of miles from land with the nearest ship around 400 miles away.

A rescue effort was being coordinated by the Reunion Islands and Australia, reports said.

Sunderland set sail in January amid criticism from some in the sailing community that her itinerary was too risky because it would place her in the Indian Ocean during the turbulent Southern Hemisphere winter.

Her father Laurence Sunderland told outdoor sports blogger Pete Thomas that he had lost contact with his daughter during a satellite phone call early Thursday before being notified by the Australian Coast Guard that both of his daughter's emergency beacons had been activated.

"Everything seemed to be under control," Laurence Sunderland was quoted as saying on the blog Pete Thomas Outdoors. "But then our call dropped and a hour later the Coast Guard called."

One of the beacons is attached to a survival suit or life raft and is only to be used when a person is in the water or aboard a life raft, reports said.

Sunderland had been bidding to follow in the footsteps of her elder brother, Zac, who arrived back in California in July last year to a hero's welcome after circumnavigating the globe in a 13-month voyage.

Zac Sunderland had been 16 when he set out on the journey, turning 17 in November 2008 before arriving home eight months later.