By Costas Paris and Benoit Faucon

Traffic mounted on both sides of the Suez Canal Thursday morning as the critical waterway remained shut while Egyptian authorities worked to refloat a grounded tanker.

Tugboats and a dredger resumed work early Thursday to dig out the Ever Given -- a 1,300-foot container ship operated by Taiwan-based Evergreen Group and owned by Japan's Shoei Kisen -- partially refloat it and move it out of the way. "The refloating drive was suspended overnight," said a senior Egyptian official. "We'll give it another go this morning."

Evergreen has hired Dutch ship-salvage specialist Smit Salvage to help with the operation. Peter Berdowski, Chief Executive of Smit parent Royal Boskalis Westminster, told Dutch state television that the operation "can take days to weeks." An especially high tide over the weekend could help efforts, according to the Egyptian official.

Officials are planning to move two ships directly behind the stranded ship to make space for the refloating process, according to a person familiar with the matter. They will also have to lighten the ship by removing some containers, fuel and ballast water, which help it steady when under way.

"In our view the situation now looks unlikely to be heading for a swift resolution," London-based Braemar ACM Shipbroking said in a note to clients on Thursday.

Danish shipping giant A.P. Moller-Maersk A/S told customers it expected a traffic backlog to grow. "The incident continues to create long tailbacks on the waterway, stopping vessels from passing and causing delays," it said in an advisory. Maersk, the world's biggest liner company in terms of capacity, said four of its vessels were stuck in the canal and another three were waiting to enter.

Suez Canal service provider Leth Agencies said Thursday that 70 northbound ships were stuck, along with another 79 southbound ships -- up from about 100 vessels combined -- were waiting late Wednesday. The World Shipping Council, a shipping trade body, said a maximum 106 ships can cross the waterway a day, and warned it could take a number of days to clear the queue of ships once the Ever Given is pushed out of the way.

The Suez Canal Authority has reopened an older part of the channel to divert some ships, but the passage can only handle smaller vessels.

"We could be here for days," said Manolis Kritikos, a mechanic at a Greek-operated tanker, stuck in the waterway. "Nothing is moving, and the radio talk is that we'll be here until the weekend."

Shoei Kisen Kaisha Ltd., the owner of the Ever Given, said it was doing its best to free the ship but "the situation involves extreme difficulty."

The Suez Canal is a vital trade route for tankers carrying oil and natural gas, along with container ships moving manufactured goods such as clothing, electronics and heavy machinery from Asia to Europe and the other way around. Around 19,000 vessels crossed the Suez in 2020, according to the Suez Canal Authority. Some 39 ships transit the Suez Canal daily on average, according to maritime industry trade group Bimco.

Shipping operators occasionally divert ships from the canal to the Cape of Good Hope around the southern tip of Africa to avoid bottlenecks, but sailings can take two weeks longer and cost cargo owners more in freight costs. Shippers said early Thursday they were already taking alternative routes to get supplies of oil, gas and other goods. Shipping costs have risen.

The cost of renting some tankers for voyages from the Middle East to Asia has jumped 47% over the last three days, as shippers seek replacements from deliveries that used to transit from Europe to Suez, said Anoop Singh, Singapore-based head of tanker analysis for shipping broker Braemar ACM.

Avoiding the canal by sailing around Africa can add $450,000 in costs per voyage, Mr. Singh said. As a result, vessels that were already at the entrance of the canal or nearby have mostly stuck with their plans so far. Braemar estimates the equivalent of 2 million barrels a day of crude and refined oil products are currently stuck at the canal -- about 2% of global oil consumption.

The Ever Given had been sailing to Rotterdam in the Netherlands from China, according to shipping data.

It was sailing northbound as part of a convoy when it got stuck in the canal at around 7 a.m. local time Tuesday, according to Gulf Agency Co., a service provider in the canal.

An Evergreen spokesperson said the ship was probably hit by strong winds causing it "to deviate from the channel and run aground."

Parts of the 120-mile long Suez Canal are a single lane stretch waterway measuring just 300-feet wide, which can require ships to travel through them in one direction at a time. Ships transit in northbound and southbound convoys. Any ship getting stuck can stop others from completing the transit.

Write to Costas Paris at costas.paris@wsj.com and Benoit Faucon at benoit.faucon@wsj.com

Corrections & Amplifications

This article was corrected at 1550 GMT because the original misspelled Manolis Kritikos' surname as Krtikos.

(END) Dow Jones Newswires

03-25-21 0744ET