Police in Pennsylvania say they "firmly believe" they have recovered the body of 2-year-old Mattie Sheils, who went missing last week during severe flash flooding.

In a press conference Friday evening, Upper Makefield Township Police Chief Tim Brewer said that "based on the physical description and the clothing found on the body, [they] firmly believe that the body of 2-year-old Mattie Sheils has been recovered, pending further identification process."

Mattie Sheils

Officials say they believe the body pulled from the Delaware River in Philadelphia Friday is that of Mattie Sheils, one of two children who went missing during flash flooding in Bucks County last week. (Upper Makefield Township Police Department)

Flashing flooding

Flash flooding developed Saturday, July 15 and lasted into the evening as rain fell around 2 inches per hour. (Upper Makefield Township Police Department)

At approximately 5 p.m., Philadelphia Police received an anonymous 911 call about a child's body in the Delaware River, near the city's wastewater treatment plant, authorities said. The anonymous caller "advised" police that there was a body in the Delaware River.

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A second caller gave authorities a physical description of a child near the Philadelphia wastewater disposal plant.

When emergency crews arrived, they discovered the child's body "in debris," Brewer said.

Sheils family

Officials say based on clothing and the physical description of the child, they strongly believe the child to be 2-year-old Matilda ‘Mattie’ Sheils. (Upper Makefield Township Police Department)

Upper Makefield Township

Crews have been searching for nearly a week for Mattie Sheils and her 9-month-old brother Conrad after they were swept away during a flash flood on Saturday, July 15. (Upper Makefield Township Police Department)

By 5:30 p.m., the child was pronounced dead and transported to the Philadelphia medical Examiner's office. Official identification is pending, and an autopsy is expected to be performed on Saturday.

Authorities said that the 2-year-old was 32 miles from where she was swept away, along with her mother, 32-year-old Katie Seley, and 9-month-old brother Conrad, in flash flooding in Berks County, Pennsylvania on July 15.

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Teams are continuing to search for Maddie's brother, Conrad, up and down the Delaware River and will continue the extensive search Saturday.

The flooding claimed the lives of five people, including Mattie and Conrad’s mother, 32-year-old Katie Seley. 

Sheils family

Teams are continuing to search for Maddie's brother, Conrad. (Upper Makefield Township Police Department)

Sheils family

Katie Seley died from the flash flooding in Burks County, Pennsylvania. (Upper Makefield Township Police Department)

Seley, her fiancé, and their three children were visiting from Charleston, South Carolina for a family barbecue when their car became one of several that was swept away. Her fiancé, mother, and 4-year-old son were able to escape the floodwaters or were later rescued.

Chief Brewer said that their "hearts are broken this evening" from the news.

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"All in all, our hearts are broken this evening," Brewer said. "Although Maddie was found 32 miles away from where she was lost, she has never been closer to all of our hearts as she is now."

"We cannot begin to fathom the pain they are experiencing, but we will never leave their side as they deal with this tragedy," he added.