NEW ORLEANS — The Coast Guard on Sunday reopened a stretch of the Mississippi River in southeastern Louisiana that was shut down as a precaution after a tugboat sank.

The Mississippi from its mouth to mile-marker 10 was reopened to alternating one-way vessel traffic after no navigation hazards were detected, the Coast Guard said in a news release. It was unclear when the stretch of river would be open to two-way traffic. Authorities were still searching for the tugboat.

One cruise ship bound for New Orleans was diverted to Mobile, Ala., and contingency plans were being made to do the same for another cruise liner that had been set to reach the city Sunday night.

The Coast Guard closed the river Saturday at 1 p.m. after the sinking of the 48-foot tug C-Pec was reported near the town of Venice. Officials don't know why the tug sank or exactly where, but Coast Guard Petty Officer Carlos Vega said it was believed to have gone down in the middle of the river.

Traffic in both directions was shut down and at one point Sunday afternoon at least 50 vessels were waiting to travel.

Two people on the tug were rescued by a good Samaritan before being transferred to a Coast Guard boat. The names and condition of those rescued were not available.

The U.S. Army Corps of Engineers and local authorities were helping with the search, which included the use of sonar.

Ownership of the downed tug was unclear. The Coast Guard said it was working to find and contact the owner. Online records indicate the vessel was owned by a limited liability corporation with a Belle Chasse, La., address, but the corporation was listed as inactive on the Louisiana Secretary of State website.

Carnival Cruise Lines diverted its ship the Conquest from New Orleans to Mobile on Sunday afternoon and passengers were to be driven to New Orleans.

The Conquest's next trip to the Bahamas has been shortened to a six-day voyage, scheduled to depart Mobile on Monday evening, Carnival said in a news release. Guests scheduled to sail on the shortened trip are being offered a one-day pro-rated refund, or a full refund if they decide to cancel their trip.

The company was making contingency plans in case another ship, the Elation, was unable to reach New Orleans on Sunday night because of the river closure, Carnival spokeswoman Joyce Oliva said in an email.