The operator of an upstate New York limousine company charged with negligent homicide in Saturday's crash that killed 20 people bore "sole responsibility" for the vehicle being on the road, authorities said Wednesday.

At an afternoon news conference, New York State Police Superintendent George Beach said Nauman Hussain knew that the 19-seat Ford Excursion limo had been ordered taken out of service after it failed an inspection last month and that the limousine's driver did not have the proper license to operate the vehicle.

"The sole responsibility for that motor vehicle being on the road on Saturday rests with Nauman Hussain," Beach told reporters.

Nauman Hussain, the 28-year-old son of Prestige Limousine owner Shahed Hussain, was arrested earlier Wednesday after a traffic stop on Interstate 787 near Albany and charged with one count of criminally negligent homicide. He was arraigned Wednesday evening in an Albany-area court and was released after posting $150,000 bond. A judge entered a not guilty plea on his behalf.

Authorities said the investigation was ongoing and more arrests and charges were possible.

Prestige attorney Lee Kindlon told reporters that Hussain "is not guilty" and claimed authorities "jumped the gun in charging him with any crime."

Schoarie County District Attorney Susan Mallery said that Hussain's car was packed with luggage when he was pulled over, to which Kindlon responded by claiming that his client felt unsafe at home because he'd gotten threats.

Hussain's arrest came four days after the Prestige-operated limousine blew through a stop sign at a T-intersection and slammed into a parked vehicle in Schoharie. All 18 people in the limousine, including driver Scott Lisinicchia, were killed along with two bystanders. The limousine was taking a group, which included four sisters and newlyweds, to a 30th birthday celebration.

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Authorities immediately launched an investigation into the crash. New York Department of Transportation spokesman Joseph Morrissey said the vehicle was cited for several code violations Sept. 4, including a problem with the antilock brakes' malfunction indicator system, and a sticker was placed on the vehicle declaring it "unserviceable." Lisinicchia, who died in the crash, also did not have the proper license to operate the vehicle.

New York Gov. Andrew Cuomo said Monday that Prestige "had no business putting a failed vehicle on the road" and said the company "has a lot of questions to answer."

Kindlon has said the issues were fixed, but Morrissey said any assertion that the limo involved in the crash had been cleared for service was "categorically false."

Even if the violations had been corrected, the owner would have needed a new inspection and new approval to transport passengers, the Transportation Department said.

Kindlon has also said that he didn't think the infractions contributed to the crash, suggesting Lisinicchia might have misjudged his momentum on a hill.

Lisinicchia’s family released a statement through a lawyer, saying the driver “never would have knowingly put others in harm’s way.”

“The family believes that unbeknownst to him, he was provided with a vehicle that was neither roadworthy nor safe for any of its occupants,” the statement read. “We ask all members of the media and public to reserve judgment on the cause of the crash until the New York State Police and the National Transportation Safety Board complete their investigations.”

Details about Shahed Hussain were also revealed in the days following the crash. Hussain was a former FBI informant who helped the U.S. government root out Muslim groups after the Sept. 11, 2001 attacks. Hussain posed as a terrorist sympathizer in at least three investigations.

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Nauman Hussain worked as the day-to-day operator of Prestige Limousine while his father is currently in Pakistan, police said. When asked if the elder Hussain would return from Pakistan to be questioned in the case, Beach said it was "not within my legal authority to ask him to come back."

In 2014, Nauman Hussain and his brother were accused by police of impersonating each other after a traffic stop. Nauman Hussain was the passenger but had a valid license. His brother did not. Police later discovered Nauman had an extensive suspension and conviction list that had been cleared, according to the Times Union.

Federal records also showed that four vehicles had been taken out of circulation by the company due to inspection failures in the past 24 months. The records list an address in Gansevoort, N.Y., that Hussain used when he filed for bankruptcy in Albany in 2003.

The crash was the nation’s deadliest transportation accident since an air crash outside Buffalo in February 2009 killed 50 people.

Fox News' Robert Gearty and The Associated Press contributed to this report.