It may not be that simple, General Stephen Townsend admitted to reporters.

“We’ll find a way to help them,” he said.

The coalition’s unexploded bombs are only a small part of Mosul’s problems. The bulk of the explosives have been hidden by IS fighters to be triggered by the slightest movement, even picking up a child’s toy, lifting a vacuum cleaner, or opening an oven door.

The effort could continue wreaking destruction on Iraq’s second largest city even as IS was defeated after a nine-month battle.

US embassy officials and contractors hired to find explosives use the same words to describe the devastation in western Mosul: historic, unprecedented, worse than any other place.

“We use broad terms like historic because when you enter a dwelling, everything is suspect,” said the team leader in northern Iraq for Janus Global Operations, a contracting company hired to find and remove hidden explosive devices and unexploded bombs from Iraqi cities recaptured from Islamic State. “You can’t take anything at face value.”

The team leader asked that he not be identified by name because he and his teams continue working in Mosul and the company fears for their safety.

Some estimates suggest it may take 25 years to clear West Mosul of explosives. The bomb-removing team leader said those understate what is sure to be a long, enduring problem.

Normalcy may return to parts of west Mosul in a year, and perhaps after a decade many of the obvious explosives will be found. But other unexploded bombs and hidden devices will surface at building sites and other locations for years and probably decades to come, he said.

As much as 90 per cent of west Mosul’s old city has been reduced to ruins, destroyed by the campaign of air strikes and ground combat needed to retake the city from IS militants who occupied it for nearly three years.

For Muhammed Mustafa, a restaurant owner from west Mosul, the disaster is very personal.

“In the beginning we thanked God we had been liberated from our oppressor,” said Mustafa, 54, who had lived in Mosul’s old city.

Mustafa escaped IS territory as Iraqi forces pushed through western Mosul earlier this year and is now living with his family in the city’s east.

“When my neighbourhood was liberated, I wanted to return and gather some belongings. On my street all I saw was destruction, except my home, thank God, but I found a written statement on the wall warning it was booby-trapped,” he said. “When I saw it, I couldn’t stand. I fell to the ground.”

Security forces in the area barred him from entering.

“They said there were many houses like it and many people had already died trying to inspect their homes when a bomb inside exploded,” he said. “Can you imagine, the house I grew up in, now I can no longer enter?”

David Johnson, vice-president for the Washington office of Janus Global Operations, said his workers are finding explosives where locals would most probably trigger them and are “seeing a level of sophistication and a number of improvised explosive devices that is literally without parallel”.

Over time, the officials said, home-made bombs have become far more innovative and sophisticated.

They range from basic pressure plates in the roads or doorways to small devices, similar to ones that turn on a refrigerator light when the door is opened. They’re said to be tucked into dresser drawers or smoke detectors, or buried under large piles of rubble that were pushed aside as Iraqi forces cleared roads to move through the city.

The devastation is so extensive and the danger so high that government and humanitarian agencies have been unable to get a full assessment of the explosives threat or a solid estimate of how much money and effort is needed to make the city safe and liveable again.

The team leader painted a grim picture of the city where his workers have spent the last two weeks trying to clear explosives from critical infrastructure, including the electricity grid.

A retired navy explosives specialist who served multiple tours in Iraq and Syria, he said his team is “facing something we’ve never seen before”.

In the navy, he said, his worst day involved finding 18 explosive devices. On Wednesday, on the outskirts of Mosul, his team cleared 50 explosive devices from a pipeline. He estimated there are as many as 300 in that one area alone.

There are five such teams made up of 130 people, working in Mosul. So far, no one has been injured. In Ramadi, however, some workers were killed and injured removing explosives. Janus wouldn’t provide details.