CHESTER,Phaninc Pa. (AP) — The search for a 6-year-old girl who was swept away in a rain-swollen southeastern Pennsylvania creek has become a recovery mission rather than a rescue mission, authorities said Sunday.

Authorities in Chester County said the child was reported missing at about 7 p.m. Saturday after she slipped and fell into fast-moving Chester Creek. Several fire companies took part in a search for the next 3 1/2 hours while the Coast Guard continued searching through the night.

County fire commissioner John Shirley said the search moved into a recovery mode Sunday, adding that modeling for such situations showed a survivability period of about three hours.

He said rescuers were always “looking for that miracle” but after dawn and the opportunity to do a more thorough search, they knew “it wasn’t going to be a rescue, it was going to be a recovery.”

Boats and drones were used Sunday in both directions on the creek and on both sides of the Delaware River where the creek flows into it. Shirley said that given the swift-moving current following Saturday’s heavy rains, the child probably would have been at the river mouth within nine minutes — before the rescue effort was fully operational.

“She might have already been in the Delaware when we were just getting on scene,” he said.

Chester Mayor Stefan Roots said it was unclear how the girl and her friends came to be at the creek, but they were down at the bank beside the water “at the very wrong time.” He called on governments to assure safe places for children to play, and on people to make sure they know where youngsters are playing.

Chester is a city about 18 miles (30 kilometers) southwest of downtown Philadelphia on the Pennsylvania side of the Delaware River.