New Jersey State Police revealed those preliminary findings on Thursday, based on initial toxicology tests.
However, the exact nature of the narcotics found in the system of 37-year-old Kevin Shelton wouldn't be available for a few weeks, police said.
In addition, police said, neither Shelton, his son 5-year-old son Cole nor his 3-year-old daughter, Cassidy, were wearing seatbelts. Cole and Cassidy were in boosters seats, police said.
Kevin Shelton and Cole Shelton were killed in crash. Cassidy Shelton was taken to the hospital in critical condition.
Shelton, of Pittsgrove, was driving westbound on Route 40 when the crash occurred around 7:00 a.m. Wednesday in the Salem County community.
Authorities say it appears Shelton's car crossed over the center line and slammed into a tractor trailer.
The vehicles collided with such force parts of the car were imbedded into the front of the 18 wheeler.
The truck's driver told a witness he kept thinking the car would return to his proper lane.
"He just said the guy kept coming over and over in his lane and there was nothing he could do," witness Harrison Godshall said.
A person who knows the family said Shelton and the children moved back to his parent's home after Cole and Cassidy's mom suffered a severe debilitating health issue.
Robert Peck, a 47-year-old Tennessee resident who was driving the truck, was not injured. He was hauling a load of paper.