Tim Nolan, president of TOTE Maritime, the ship's owner, said the "the entire TOTE Maritime Puerto Rico family is distressed that it now appears the El Faro sank at or near its last known position."
"We continue to hold out hope for survivors," he said.
Three more Americans were identified among the 33 people on board the container vessel.
South Florida men Jeremy Riehm, 46, and Steven Shultz, 51, were named by their families as among the missing, according to NBC affiliate WBBH. A third American was identified as Keith Griffin.
Shultz's mother told WBBH that she believes her son, a Merchant Marine for 30 years, is alive along with the rest of the crew, but is worried that supplies are running out.
Other missing American crew members include 51-year-old Mariette Wright, engineer Mike Holland and Second Mate Danielle Randolph. "