Searchers say they have grave concerns for seven people aboard an American schooner that disappeared earlier this month between New Zealand to Australia.

Maritime New Zealand said Thursday that searches by plane this week found no sign of the 70 foot (21 meter) vessel named Nina.

Authorities say there are six Americans — three women and three men — and one British man aboard. The schooner was built in 1928.

It left the Bay of Islands in northern New Zealand on May 29.

Authorities say the last communication was on June 4, when the Nina was about 370 nautical miles west of New Zealand. A storm that day saw winds gusting up to 110 kilometers (68 miles) per hour and waves of up to 8 meters (26 feet).