PARADISE, Calif. — The long, laborious process of returning Paradise and neighboring towns to a safe state will begin next month when crews in masks, Tyvek suits and booties begin combing through every last property in this town that was decimated by wildfire. Their targets are things like burned bottles of bleach, melted cans of paint, and corroded car batteries, which will be tagged and removed.

Next, they will test the surrounding soil and, if needed, scrape away layers to get to clean earth, free from oil and gasoline. “You’d be surprised how much of that stuff survives a fire,” said Adam W. Palmer, an environmental scientist with the California Department of Toxic Substances Control who is helping lead the cleanup.

In the charred footprint of each home in Paradise lurks an invisible and dangerous legacy of the Camp Fire: toxic chemicals released by the blaze. There may be radioactive isotopes from burned-up antique crockware, cupboards of incinerated household cleaners, and asbestos from old siding. Heavy metals, chemicals and biological contaminants left behind demand a cleanup of extraordinary scale, before any permanent return to Paradise is safe, according to the department.

Only once the properties have received official signoff that they have been cleansed can residents begin rebuilding. The task will take time; cleanup is still not finished in the aftermath of the Tubbs Fire, which scorched Sonoma, Napa Valley, and other parts of Northern California over a year ago. The Camp Fire destroyed more than three times as many buildings than did the Tubbs Fire.