New York (CNN) -- Investigators found a sleeping-aid drug in Kerry Kennedy's blood after a recent car accident, according to court documents.
The final toxicology results show no alcohol and no drugs other than zolpidem, the generic name for Ambien.
"Moments after the accident occurred, I told police that it was possible that I may have inadvertently taken a sleep aid instead of my daily thyroid medication," Kennedy said in a statement released Wednesday.
Police found Kennedy, 52, daughter of the late Robert F. Kennedy and ex-wife of New York Gov. Andrew Cuomo, behind the wheel of her damaged Lexus SUV on the morning of July 13.
A New York State Police press release said the SUV collided with a tractor-trailer.
At a court hearing on July 17 in North Castle, New York, Kennedy pleaded not guilty to charges of driving while impaired.
At a news conference after her court appearance, Kennedy said a partial seizure was the cause of the accident -- a seizure she said might have been from a previous injury she suffered on the right side of her brain.
The judge released her under her own recognizance.
She submitted to both blood and urine tests after the accident.
Kennedy said she visited Mount Sinai Medical Center, where she underwent "a full battery of neurological testing" to understand her medical condition.
Lucian Chalfen, a spokesman for the district attorney's office in Westchester, declined to comment Wednesday, citing a pending case.
In her statement, Kennedy said, "I am deeply sorry to all those I endangered that day, and am enormously grateful for the support I have received over the past two weeks."
According to the clerk for North Castle Justice Court, Kennedy's case is adjourned until August 14.
CNN's Dominique Debucquoy-Dodley contributed to this report.