As many as 40 people were hurt when a New Jersey Transit bus rear-ended a bus carrying Canadian students Wednesday morning in the Manhattan-bound Lincoln Tunnel, the Port Authority said.

None of the estimated 35 to 40 injuries was considered life-threatening, Port Authority spokesman Joseph Pentangelo said. Four people who suffered neck and back injuries were removed on backboards and stretchers, he said.

A 32-year-old woman, whose vehicle was stuck behind the two buses, went into labor after the crash and was taken to Bellevue Hospital Center, Pentangelo said. He said a second pregnant woman refused medical attention at the scene.

Pentangelo said 22 of the injured went to Bellevue while the rest went to Lenox Hill Hospital.

New Jersey Transit said about 60 passengers were on its bus. A spokeswoman from the Toronto District School Board told The Associated Press there were 26 students and two adults from a Toronto school headed to New York for a graduation trip aboard the private charter.

Pentangelo said that bus was being operated by Denny's Bus Lines, located in Acton, Ontario, Canada.

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The crash occurred in the Manhattan-bound center tube at 9:35 a.m., Pentangelo said.

The center tube was reopened about 11:40 a.m., Pentangelo said. He said the crash caused extensive delays and forced officials to reroute traffic through another of the three tunnel tubes. It was not clear how many of the injuries occurred on each bus.

With Maria Alvarez

and AP