Canada's Foreign Affairs department says there weren't any Canadians among the four people killed in Saturday's bus crash in New York state.
A department official also says no Canadians were seriously injured when the double-decker bus failed to clear a low-hanging bridge near Syracuse, N.Y.
At least seven Canadians, all from Ontario, were among the 28 passengers on the Megabus, which was bound for Toronto.
Police in New York say three of the dead were men, the fourth a woman in her late teens or early 20s.
The bus was not on the route it normally takes on its Philadelphia-to-Toronto run, but it's not yet known why that was the case.
The driver survived the crash, but is in hospital.
A Canadian on a double-decker said a terrific jolt catapulted her across several seats when the bus rammed into a bridge, killing four people.
"I fell over, was thrown over people, and then it was all quiet," said Vicky Reed, 71, from Dundas, Ont. "The top of the bus had been pushed back just like an accordion."
Don Carmichael, senior vice-president for Coach USA, which operates Megabus, said the details of the incident were still "sketchy." He didn't know why the bus with 28 passengers had gone off its prescribed route when it crashed.
"It is not an alternative route prescribed, that's going to be part of our investigation," he said. "We really have no idea why it was on that route."
Mr. Carmichael said the bus driver had driven the route "a number of times" and would have known the proper routing to come off Interstate 81 for a scheduled stop at the Regional Transportation Centre in Syracuse.
Many of the passengers aboard were rushed to various area hospitals with injuries that reportedly ranged from minor to serious.
Ms. Reed said the four passengers who were killed were seated at the top of the bus, near the front, right where the vehicle would have crashed into the low-hanging bridge.
"The bus was too tall and so it sort of ripped the top of the front part of the bus off," said Ms. Reed. "The bus was then sort of on its side."
Ms. Reed, who suffered a knee injury from the crash, recalls seeing one woman whose face was covered in blood and another with a leg trapped under a piece of metal who was moaning in pain.
Meanwhile, the driver, who has been doing the job since Dec. 2009, emerged from a cloud of concrete dust, injured, but alive.
"His face looked like it had been cut with razor blades, he couldn't understand what happened, he was ... in shock," said Ms. Reed.
Richard Blansett with the Red Cross of central New York said his organization was providing support to rescuers as well as those who survived the crash. He said there were still passengers being treated at four different hospitals, with some requiring surgery.
At least 14 passengers were released and were at a Syracuse hotel where the Red Cross was providing them with meals and emotional support.
Mr. Blansett said he had personally spoken to four Canadians who were on board the bus, while they were recuperating at the hotel.
Red Cross workers met with passengers to help them cope with the emotional toll of the crash, Mr. Blansett said.
"They're folks who've been through a very, very arduous experience," he said. "They're in a very fragile state and we're trying to do everything we can to provide emotional support and the physical support they need."
The bus left Philadelphia on Friday night. It had been scheduled to stop in Syracuse and Buffalo on its way to Toronto.
Photographs from a local television station showed the top level of the bus crushed and partially peeled back in the front. The double-decker struck the bridge span between two large signs warning that the clearance was 10 feet, 9 inches.
Mr. Carmichael said the fatal crash is the first such incident for Megabus since its launch in 2006.
"We have extremely high standards of safety and we've transported in excess of seven-million people and never an incident like this, " he said.
The department of Foreign Affairs said the Canadian mission in Buffalo, N.Y., was working with local authorities to provide consular assistance to affected Canadians as required.
The bus line said it would co-operate fully with authorities to figure out how the crash occurred. The company also said it would transport the passengers who have been released from hospital to their final destinations.
A spokesman for the New York State Department of Transportation said the railway bridge where the accident occurred had been the site of previous mishaps.
"Over the years there have been several incidences where tractor trailers have become wedged under the bridge and had to be backed out," Gene Cilento said, noting there had previously been "no fatalities associated with it."
Mr. Cilento called Saturday's accident "extremely serious."
He said local and state police will investigate the accident and the department of transportation will look into any safety recommendations as a result.