Story highlights The Nina has given off no signs of life since early June

The racing schooner built in 1928 had seven passengers on board

Six Americans and one Briton are missing

The ship is equipped with modern tracking and communications devices

A historic racing sailboat and its crew of seven, including six Americans, have apparently vanished on the high seas.

A wooden schooner built in 1928, the Nina, left port in northern New Zealand at the end of May and dropped out of communication a week later, a maritime safety authority said Thursday.

It was en route to Newcastle, Australia.

The sailing yacht is equipped with a tracking device, a satellite phone and an emergency buoy, but none of them have been heard from since early June, according to Maritime New Zealand.

At the time of its last sign of life, the Nina was nearly 400 miles northwest of New Zealand in the Tasman Sea.

Family members alerted maritime authorities in New Zealand in mid-June that the sailboat may be missing. Rescuers issued alerts to vessels in the area. None reported having seen the Nina.

Two extensive sweeps by a reconnaissance plane came up empty.

The Nina was carrying one British passenger along with the six Americans.