The driver, 66-year-old Paul Vanalfen, and 38-year-old Charlene Lloyd, died after their 2008 Camry crashed into a rock wall in Wendover, Utah, on November 5.
Two other family members were injured in the accident and admitted to hospital, but have been released.
Highway patrol Sergeant Nathan Croft told reporters the skid marks on the road revealed the driver tried unsuccessfully to stop the car before an intersection as it left a highway.
He said there did not appear to be anything wrong with the vehicle’s brakes.
Millions of Toyota Motor Corp. vehicles have been recalled in the past 12 months over issues with sticking accelerator pedals and floor mats that could interfere with the pedals.
The National Highway Traffic Safety Administration received reports of up to 93 sudden acceleration-related deaths over the past decade from Toyota drivers, however only four have been confirmed by the US Government.
Sgt Croft confirmed Mr Vanalfen’s Camry had undergone one mandatory recall for a sticking accelerator pedal, but it was still uncertain whether two voluntary repairs to correct a sticky floor mat and a short accelerator pad had also been completed.
He said police and investigators suspected one of those issues could have caused the crash.
“We can’t say definitely, but there is a strong likelihood that that in fact did cause the crash,” he said.
The police report also noted two of the passengers, Ms Lloyd and her fiancé, Cameron Vanalfen, were not wearing seatbelts.
Toyota responded by expressing its sympathy to those affected by the accident. Spokesman Paul Nolasco said Toyota was supporting police with the investigation and said it was too early to draw conclusions from the incident.
No Toyota or Lexus vehicles sold in Australia were affected by the accelerator pedal or floor mat recalls. Toyotas sold in Australia sourced related components from different suppliers.