The Suez Canal remained shut Thursday as Egyptian authorities worked to clear a ship blocking the critical waterway and shipping experts warned a resumption of traffic through the channel could be days away or longer.

Tugboats and a dredger resumed work early Thursday to dig out the Ever Given—a 1,300-foot ship operated by Taiwan-based Evergreen Group—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.