A Navy search vessel that departed from Virginia on Monday afternoon will face weather delays as it heads toward the Bahamas to locate the wreckage of the El Faro, the cargo ship that sank this month with a crew of 33 that included four Mainers.

The 790-foot El Faro is believed to have sunk in the Atlantic Ocean sometime after Oct. 1, when it lost propulsion in the path of Hurricane Joaquin on a routine voyage from Jacksonville, Florida, to San Juan, Puerto Rico. Five of the crew members, including all the Mainers, were graduates of the Maine Maritime Academy, including Capt. Michael Davidson of Windham.

The USNS Apache, an oceangoing tug carrying sonar equipment and a remotely operated submersible vehicle, was forced to take an alternate route from Norfolk toward the wreckage site to avoid bad weather, Naval Sea Systems Command spokesman Chris Johnson said after the Apache’s departure.

Johnson said the Apache is now expected to arrive at the wreckage site off Crooked Island in the Bahamas in about one week rather than on Wednesday or Thursday as the Navy had originally planned.

The delays will cut into the amount of time the crew aboard the Apache will have to use a hydrophone, a device used to detect underwater sound, to listen for pinging emitted by the El Faro’s voyage data recorder, commonly called the “black box.” The recorder is the primary focus of the search and could answer key questions about what happened to the ship and why.

The batteries in the black box are designed to last 30 days after the device hits the water, meaning they are likely to run out a matter of days after the Navy ship reaches the search site. After the batteries die, the Apache crew would have to use sonar to scan underwater in the area where the El Faro is believed to have gone down.

“We will have four solid days to use the hydrophone,” Johnson said. “We’ll start trying to use the hydrophone to look for the black box. But if not, sonar is our next option.”

Peter Knudson, a spokesman for the National Transportation Safety Board, confirmed on Monday that one of its investigators is on board the Apache.

The National Transportation Safety Board, which is leading the investigation into the El Faro’s sinking, is focusing on final communications between the ship’s captain and its owner, TOTE Maritime Puerto Rico.

Those communications would likely have been preserved on the black box, a 55-pound, suitcase sized recorder.

“Our primary mission is to recover the black box,” Johnson said.

Although time is running out to track the pinging being emitted by the black box, Johnson said investigators are “fairly confident” that they will be able to locate the El Faro.

The Navy is focusing on roughly 100 square miles of ocean floor off Crooked Island, a search area about two times the size of Portland.

“It’s a relatively small search area,” Johnson said.

If the Apache locates the El Faro, its crew will use an unmanned, remotely operated underwater vehicle, called the CURV-21, to search using its onboard sonar, cameras and mechanical arms.

The El Faro’s black box will likely be in its control cabin, but depending on how the ship struck the ocean floor it could make the cabin more difficult to access, he said.

“It is challenging,” Johnson said.

The El Faro set sail from Jacksonville on Sept. 29 carrying containers topside and trailers and vehicles below deck. At the time of its departure, Tropical Storm Joaquin had not been upgraded to hurricane status. The El Faro proceeded on its course until Oct. 1, when it lost propulsion, stranding the vessel in the path of what became Hurricane Joaquin, a Category 4 storm that brought 50-foot seas and 130 mph winds. Officials believe the ship sank northeast of Crooked Island in roughly 15,000 feet of water.

The Coast Guard searched for six days after final communication from the El Faro and located one body it wasn’t able to recover, a damaged lifeboat and other debris.

Johnson said that while recovering the black box is the primary mission, the Apache’s crew will try to recover any human remains if possible.

In addition to Davidson, the captain from Windham, four other crew members were Maine Maritime grads: Danielle Randolph of Rockland, Mike Holland of Wilton, Dylan Meklin of Rockland and Mitchell Kuflik of Brooklyn, N.Y.

In another development Monday, a second lawsuit was filed on behalf of an El Faro crew member who was on board when it sunk.

A lawyer for Tina Riehm, widow of third mate Jeremie Riehm, filed the suit in Florida, The Associated Press reported.

Last week, the family of Lonnie Jordan filed a $100 million lawsuit against TOTE Maritime and its captain.

Riehm’s lawsuit alleges that the captain failed to take a safer route away from bad weather because he wanted to deliver the cargo on time.

The company says it is not commenting on any individual lawsuits brought in the El Faro case.