BOSTON -- Investigators trying to learn why a commercial fishing boat sank off Massachusetts nearly a year ago, taking the lives of all four crew members, are using some high-tech gadgetry in their probe, federal authorities said Wednesday.

       The 82-foot (25-meter) Portland, Maine-based Emmy Rose went down early Nov. 23 as it was heading to port after a seven-day fishing trip, the National Transportation Safety Board said in a statement. Authorities have previously said it was heading to Gloucester, Massachusetts.

       The Emmy Rose was located in May, in an upright position with its outriggers deployed, in about 800 feet of water on the seafloor about 25 miles off Provincetown, Massachusetts, the NTSB said.

       To aid in the investigation, federal authorities partnered with the National Science Foundation and the Woods Hole Oceanographic Institution in September to survey the sunken vessel using a remotely operated vehicle.

       The vehicle yielded videos and high-resolution photos that are being used by investigators trying to determine why the vessel went down. It remains under investigation.

       The vessel made no distress calls. The Coast Guard searched more than 2,200 square miles over a 38-hour period, yet found nothing more than a debris field, diesel fuel odor, an emergency beacon and an empty life raft.

       The crew — Capt. Robert Blethen Jr., of Georgetown, Maine; Jeffrey Matthews, of Portland, Maine; Ethan Ward, of Pownal, Maine; and Michael Porper, of Gloucester, Massachusetts — was never found.