The pair, a man and a woman, approached a homeowner in the township's Oakford section about seal-coating their driveway, authorities said.
When they were turned down, they said the woman was pregnant and asked if she could use the homeowner's bathroom, according to police.
The homeowner obliged but later noticed multiple pieces of jewelry missing, investigators said.
They were driving a red Ford pickup truck with the bumper and grill both painted red. The truck bed had no liner and contained seal-coating equipment, police said.
Oakford section residents are asked to check their home security systems for footage of the truck. Anyone with information can call Lower Southampton Township Police 215-357-1234 or submit a tip through Crimewatch.
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