SUEZ, Egypt -- Two additional tugboats deployed Sunday to Egypt's Suez Canal to aid efforts to free a skyscraper-sized container ship wedged for days across the crucial waterway, even as major shippers increasingly divert their boats out of fear the vessel may take even longer to free.

The MV Ever Given, a Panama-flagged, Japanese-owned ship that carries cargo between Asia and Europe, got stuck Tuesday in a single-lane stretch of the canal. In the time since, authorities have been unable to unstick the vessel and traffic through the canal -- valued at more than $9 billion a day -- has been halted, further disrupting a global shipping network already strained by the coronavirus pandemic.

The Dutch-flagged Alp Guard, a specialist tugboat, arrived at the location Sunday, according to the stuck ship's technical management company, Bernard Schulte Shipmanagement. The Italian-flagged tugboat Carlo Magno was also close, having reached the Red Sea near the city of Suez early Sunday, satellite data from MarineTraffic.com showed.

The tugboats, along with at least 10 others already there, will be used to nudge the quarter-mile-long Ever Given as dredgers continue to vacuum up sand from underneath the vessel and mud caked to its port side, Bernhard Schulte said.

Excavators dug Sunday on the eastern wall of the Suez Canal, hoping to free the bulbous bow of the Ever Given that plowed into the embankment, satellite photos showed. Bernard Schulte said the team was also waiting for the arrival of additional equipment to dredge the canal's seafloor. The THSD Causeway, a dredger registered in Cyprus, was expected to arrive by Tuesday.

This satellite image shows the cargo ship MV Ever Given stuck in the Suez Canal on Saturday near Suez, Egypt.Maxar Technologies via AP

Authorities canceled Sunday's planned freeing attempts "until sufficient tug power is in place," said canal services firm Leth Agencies. They plan to conduct an effort to free the vessel today to coincide with high tides, it said.

Officials have been desperately trying to avoid unloading the vessel, which likely would add even more days to the canal's closure. Taking containers off the ship would require a crane and other equipment that have not arrived.

On Saturday, the head of the Suez Canal Authority told journalists strong winds were "not the only cause" for the Ever Given running aground, appearing to push back against conflicting assessments offered by others. Lt. Gen. Osama Rabei said an investigation was ongoing but did not rule out human or technical error.

Bernhard Schulte Shipmanagement maintains their "initial investigations rule out any mechanical or engine failure as a cause of the grounding." However, at least one initial report suggested a "blackout" struck the hulking vessel carrying some 20,000 containers at the time of the incident.

Rabei said he remained hopeful dredging could free the ship without having to resort to removing its cargo, but added "we are in a difficult situation, it's a bad incident."

Asked about when they expected to free the vessel and reopen the canal, he said: "I can't say because I do not know."

Speaking on Sunday to the pro-government Egyptian television channel Extra News, Rabei said Egyptian President Abdel Fattah el-Sissi had ordered the canal authority to prepare for all options, including taking containers off of the vessel. He said officials had been in talks with the U.S. about that possibility, without elaborating.

Shoei Kisen Kaisha Ltd., the company that owns the vessel, said it was considering removing containers if other refloating efforts failed.

The Ever Given is wedged about 3.7 miles north of the canal's Red Sea entrance near the city of Suez.

A prolonged closure of the crucial waterway would cause delays in the global shipment chain. Some 19,000 vessels passed through the canal last year, according to official figures. About 10% of world trade flows through the canal. The closure could affect oil and gas shipments to Europe from the Middle East. Already, Syria has begun rationing the distribution of fuel in the war-torn country amid concerns of delays of shipments arriving amid the blockage.

As of early Sunday, over 320 ships waited to travel through the Suez, either to the Mediterranean or the Red Sea, according to canal services firm Leth Agencies. At least 10 of those vessels carried livestock, raising concerns about the animals. Rabei told the Saudi-owned satellite news channel Al-Arabiya authorities planned to offer provisions to help them.

Dozens of others still listed their destination as the canal, though shippers increasingly appear to be avoiding the passage.

The world's biggest shipping company, Denmark's A.P. Moller-Maersk, warned its customers it would take anywhere from three to six days to clear the backlog of vessels at the canal. Already, the firm and its partners have 27 ships waiting to enter the canal, with three stuck in the waterway itself and two more that were to come Sunday.

"We have until now redirected 15 vessels where we deemed the delay of sailing around the Cape of Good Hope at the southern tip of Africa equal to the current delay of sailing to Suez and queuing," the shipper said.

Mediterranean Shipping Co., the world's second-largest shipper, said it already had rerouted at least 11 ships around the Cape of Good Hope to avoid the canal. It turned back two other ships and said it expected "some missed sailings as a result of this incident."

"MSC expects this incident to have a very significant impact on the movement of containerized goods, disrupting supply chains beyond the existing challenges posed by the COVID-19 pandemic," it said.

Associated Press writer Jon Gambrell reported this story from Dubai, United Arab Emirates, and AP writer Samy Magdy reported in Suez. AP writers Isabel DeBre and Malak Harb in Dubai contributed to this report.