Mayor Mitch Landrieu has requested the New Orleans City Council pass an emergency declaration to hire contractors to repair the massive hole that opened near the foot of Canal Street..

The declaration is the first step toward repairing the more than 20-foot-long chasm near the Shops at Canal Place, which opened up last Friday after the wooden wall of an underground tunnel gave way.

If, as expected, it is passed by the City Council, the administration will begin seeking bids for the repairs, which are estimated to cost $3 million to $5 million and will take between 3 months and 6 months to complete.

City officials and engineers speculated last week that the wall of the tunnel, which runs underneath Harrah’s Casino to Poydras, had been weakened by water leaking out of a drainage pipe that ran above it. But city officials do not yet know what directly caused the collapse, Landrieu spokesman Hayne Rainey said in an email.

Engineers from the Sewerage and Water Board, Regional Transit Authority, AT&T, Harrah’s Casino and city consultants Hatch Mott McDonald and Eustis are working on developing a plan for repairs, Rainey said.

The first step in any repairs will be removing the overhead lines that power the Canal Streetcar.

The state Department of Transportation and Development has offered assistance on the repairs, though it is taking a supporting role. Secretary Shawn Wilson said Wednesday the department would be looking to provide any technical support necessary and could help the city find money for the repairs.

Follow Jeff Adelson on Twitter, @jadelson.