Full restoration of electricity to some of the hardest-hit areas of Louisiana battered by Hurricane Ida could take until the end of the month, the head of Entergy Louisiana has warned.

At least 16 deaths were blamed on the storm in Louisiana, Mississippi and Alabama.

Ida damaged or destroyed more than 22,000 power poles, more than hurricanes Katrina, Zeta and Delta combined – an impact Entergy president Phillip May called “staggering”.

More than 5,200 transformers failed and nearly 26,000 spans of wire — the stretch of transmission wires between poles — were down.

Mr May said: “The level of devastation makes it quite difficult or near impossible to get in and fully assess some places.”

The company is estimating full power restoration by September 29 or even longer for some customers.

Entergy New Orleans president Deanna Rodriguez said about a quarter of New Orleans residents have power back, including all the city’s hospitals, and the city’s 27 substations are ready to serve customers.

One of the parishes facing long delays for power restoration is Terrebonne, where volunteers in the parish seat of Houma handed out ice, water and meals to shell-shocked storm survivors on Saturday. Houma is roughly 55 miles (90 kilometres) southwest of New Orleans.

Some parishes outside New Orleans were battered for hours by winds of 100 mph (160 kph) or more.

By Saturday morning, 97% of damage assessment was complete and power restored to about 282,000 customers from the peak of 902,000 blacked out after Ida.

The lower Mississippi River reopened to all vessel traffic in New Orleans and ports throughout southeastern Louisiana after power lines from a downed transmission tower were removed, the Coast Guard said.

New Orleans mayor LaToya Cantrell said the city was offering transportation to any resident looking to leave the city and get to a public shelter.

By the end of Saturday, city agencies conducting wellness checks had evacuated hundreds of people out of eight senior living complexes where officials deemed conditions unfit for living.

The coroner’s office is investigating four post-storm deaths that occurred at three of those facilities.

As recovery efforts continued, state officials were monitoring a system of disturbed weather in Mexico’s Bay of Campeche, which appeared set to move into the Central Gulf of Mexico closer to Louisiana.

Louisiana Governor John Bel Edwards said the state is planning an exercise to assess its emergency response if needed.

Predictions so far do not show the system strengthening into a hurricane, but he said “even if it’s a tropical storm, we’re in no state to receive that much rainfall at this time”.

He said: “We can’t take the playbook we normally use because the people and assets are no longer where they would have been.

“How do you staff up shelters you need for the new storm and continue to test for Covid? My head’s getting painful just thinking about it.

“We will be as ready as we can be, but I’m praying we don’t have to deal with that.”

Meanwhile, Coast Guard crews were responding on Saturday to a sizeable oil spill in the Gulf of Mexico following the storm.

The ongoing spill appears to be coming from an underwater source at an offshore drilling lease about two miles (three kilometres) south of Port Fourchon, Louisiana.