More than 30 people were injured this morning in a Lincoln Tunnel crash where a New Jersey Transit bus rear-ended a private bus carrying elementary students snarling traffic for hours, officials said. The accident, which sent more people to the hospital than any other accident in the tunnel this year, happened at about 9:35 a.m. and caused hour-long delays for some drivers heading into New York City, according to the Port Authority of New York and New Jersey. Twenty-six Canadian eighth-grade students, the school's principal and another staff member were on the charter bus heading into New York for a day of sightseeing, according to officials at Toronto School District Board. All were uninjured. Suffering mostly neck and back injuries, 31 passengers were transported to Bellevue, Lenox Hill and Mount Sinai Roosevelt hospitals in the city, according to Joe Pentangelo, Port Authority Police's public information officer. None of the injuries appeared to be life threatening, Pentangelo said. Four were taken away on stretchers. A handful of other passengers were treated on scene or refused medical attention. A 32-year-old woman stuck in the traffic while riding on a separate NJ Transit bus in the tunnel went into labor around 10:45 a.m. and was transported to Bellevue Hospital Center, according to Pentangelo. The accident closed traffic through the center tube of the tunnel for over two hours and vehicles was rerouted to the southern tube. It was cleared by noon and the agency cancelled the traffic alert for the tunnel. All lanes have been reopened and should not affect evening commute. Nancy Snyder, a spokeswoman for NJ Transit, said the agency's bus was on the 166 line with 60 passengers on board. The bus line was headed for Port Authority Bus Terminal after stops in Hudson and Bergen counties. The Port Authority is investigating the accident. The bus that was rear-ended was a 56-passenger bus with a Canadian charter bus company based out of Toronto, Brain Denny of Denny's Bus Lines said. The principal of Toronto elementary school Bedford Park tweeted out that no one on board was injured.