DAKAR, Senegal — Rescuers in Sierra Leone’s capital said on Friday that it was unlikely any of the hundreds of people buried in mudslides this week were still alive, after torrential rains that hit the country’s capital left more than 400 people dead.

A search and rescue mission that had been carried out since heavy rains triggered the collapse of a hillside and caused muddy rivers to flow through the streets of Freetown, the capital, has now all but turned into an effort to recover bodies, emergency responders and aid groups said.

More than 600 people are believed to be missing, with many still trapped under tons of mud that some residents, facing a shortage of heavy equipment, took to digging through with their bare hands. Sierra Leone’s ministry of health and other groups leading the search called on Friday for more volunteers to help find victims.