Police said the deadly fumes came from a car left running in the Milford Township home's attached garage, WPVI-TV, Philadelphia, reported. State police were investigating whether the deaths were somehow a murder-suicide case, the TV station said.
The bodies of Gary Reitnauer, 59, Michele Reitnauer, 58, and their daughters, Yun Jiao (Kimberly) Cao, and Jamie Hongfan Reitnauer, 10, were found about 11:20 p.m. Monday.
Troopers found Gary Reitnauer in the car. Michele Reitnauer and one of the girls also were found in the garage and the second daughter was found elsewhere in the home.
A nephew, Rob Zem, told WPVI-TV the deaths came as a shock.
"I don't know what went wrong. It's a tragedy all around," he said.