A family from South Carolina who got caught in deadly flash flooding in eastern Pennsylvania over the weekend is asking the public to "pray for the return" of a missing nine-month old boy and his two-year-old sister. 

The whereabouts of Conrad and Matilda "Mattie" Sheils remain unknown Tuesday as the Upper Makefield Township Police Department is vowing to "continue to search for these beautiful children." Their mother, 32-year-old Katie Seley, was identified by the Bucks County Coroner as one of five people who died in flooding that police say was caused by a "torrential rainstorm" on Saturday. 

"Our family would like to extend our deepest gratitude for the enormous efforts of so many emergency personnel who have been working tirelessly, in dangerous and difficult conditions, to rescue the victims of this horrific tragedy," the Sheils family said in a statement, through a spokesperson. "Their compassion, kindness, and bravery have given us strength in this unspeakably difficult time, and their commitment to bringing Conrad and Mattie home is unwavering." 

"We ask that you continue to pray for the return of Conrad and Mattie and for the safety of all of those committed to bringing them home to us," the statement added. 

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Flash flooding Pennsylvania missing children

Matilda Sheils, 2, and Conrad Shiels, who is 9 months old, remain missing Tuesday following flash flooding over the weekend in eastern Pennsylvania. (Upper Makefield Township Police Department)

Upper Makefield Township Police say the Shiels family, from Charleson, were in the area visiting family and friends and were on their way to a barbecue when "their vehicles got caught in the flash flood on Rt. 532." 

The father, identified as Jim Sheils, "miraculously, was able to get himself and their 4-year-old son to safety, but the mother and grandmother who were trying to get their 2 other children, ages 9 months and 2 years to safety, were all swept away by the raging flood waters.   

"Unbelievably, the grandmother survived and was treated at a local hospital," police said. "However, the lovely mother of these two beautiful children was one the people we found deceased during.... search efforts. So, it is their two children we are looking to bring home." 

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South Carolina family trapped in Pennsylvania flooding

Police say Jim Sheils and the couple's 4-year-old son managed to survive, while mother Katie Seley died in the flooding. (Upper Makefield Township Police Department)

Police described the deaths in Pennsylvania as "a mass casualty incident the likes of which we have not seen before." 

The other victims were identified as Enzo Depiero, 78, Linda Depiero, 74 and Yuko Love, 64, of Newtown Township and Susan Barnhart, a 53-year-old female from Titusville, New Jersey. 

"There was another massive search operation conducted in the area of the flash flood in an effort to locate Conrad and Mattie," police said Monday. "Regretfully, today’s operation did not result in us bringing them home to their family." 

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Eastern Pennsylvania road flooding

A view of flooding over the weekend along Rt. 532 in eastern Pennsylvania. Police said "this wasn’t the worst section of the flooding along Rt. 532." and "that was further up the road where are the vehicles had been trapped." (Upper Makefield Township Police Department)

Police also said "that the people who got caught in the flash flood did NOT drive into a flooded roadway. 

"The water came upon them and that there was nothing they could have done to avoid the suddenness of the raging water," it added.