On Monday, investigators continued to search for clues as to what caused the 2001 Ford Excursion limousine to speed down a rural highway, through a stop sign and into an unoccupied car, killing 17 friends in the vehicle who were on their way to celebrate a birthday party. An assistant professor of geology at the State University of New York, Brian Hough, and his father-in-law were struck and killed as they stood near a parking lot at the base of the hill, according to Syracuse.com and Facebook posts.

In a briefing at a regional headquarters of the State Police outside Albany, Robert L. Sumwalt, the chairman of the National Transportation Safety Board, said that his agency’s inquiry was focusing on mechanical and human causes for the accident and that there was extensive damage to the front and left side of the limousine.

He suggested that the engine of the Excursion had been thrust backward into the driver’s compartment, saying the evidence indicated a “high-energy impact.” But he declined to say definitively that the vehicle had been speeding; there were no skid marks leading to the crash site.

Investigators also said they had recovered an airbag control module, which was being analyzed for crash data.

State Police officials suggested that the company had been on their radar before the crash. “That company and that vehicle have been under scrutiny” in the past, said Maj. Robert Patnaude of the New York State Police. He also suggested that Mr. Hussain could face criminal charges. “That will be part of our investigation,” Major Patnaude said.

The investigation will also include autopsies of the victims, a tight-knit group that included four sisters, two brothers and several young couples. Those victims had yet to be identified by the authorities but heartbroken friends and relatives were already posting testimonials.