U.S. federal investigators say the Toronto tour bus that overturned on a New Jersey highway off ramp on the weekend was not permitted to be travelling in the United States.

The Federal Motor Carrier Safety Administration, part of the U.S. Department of Transportation, said it is investigating the Canadian company and the bus driver as part of its probe into the incident.

Twenty-three passengers were sent to nearby hospitals with injuries after the bus lost control, veered off the road and overturned in Wayne, N.J., Saturday morning.

According to hospital officials, three passengers remained in hospital in fair condition on Monday afternoon.

Police said the group was travelling with Cynthia’s Bus Tours, which had rented the bus from AVM Max 2000 Charter Services Inc.

According to the safety administration, the same bus company is registered under the name AYM Max Charter Services Inc., and has “no current operating authority” in the U.S. because its insurance expired in July.

"Safety is our number one priority," the federal agency said in a statement on Monday.

"While (the company) has a satisfactory safety rating, it does not have the authority to operate in the U.S. due to an unresolved lapse in its insurance coverage. This compliance violation is one of the factors we will evaluate as part of our post-crash investigation of the carrier and driver."

Department records also showed that the company had a number of previous citations dating back to April 2011, including five for fatigued driving violations.

In one case from last May, a driver was allowed to be on the road for more than the permitted 11 hours.

Many of the passengers on the bus that overturned Saturday were travelling to a religious event in Brooklyn.

The bus passengers, many who were sleeping at the time the bus overturned, described the crash as terrifying and chaotic.

“The bus was laying on its side. There was no window and the door was still closed, so people wanted to get out,” passenger Warren Lawrence told CTV News on Sunday.

Lawrence helped pull 15 people to safety through the vehicle’s roof as it lay on its side in a small marsh off the highway.

At least three passengers were pinned to the ground by window frames until they were freed by emergency workers.

State police said it will take at least two weeks before they determine what caused the bus to overturn.

The bus driver, Brampton resident Neville Larmond, told authorities that he veered off the highway after he was cut off by another vehicle. However, investigators have not verified Larmond’s statement.

"If that's the statement he gave, that will be something we will investigate and try to corroborate any witness statements," said Sgt. Adam Grossman of the New Jersey State Police.

With files from The Canadian Press