Patrick Michel, the captain of a yacht which has joined the search for the missing British sailors, said a member of his crew saw a "wooden plank about 1m long, 20-30cm wide, and another rectangular white foam or plastic [object]."
He said he had "no idea if it is part of the boat" but that he had emailed the details to the US Coast Guard.
The sighting was made at around 10pm UK time last night for "a brief second, and then it vanished into the night."
With no sign of a life raft or of debris, and with nearly 20,000 square miles having been searched, the hunt continues for another day.
Veteran yachtsman Tony Bullimore tells ITV News that there is a "strong possibility" the yachtsmen are still alive in the life raft.