Someone shouted 'duck' before charter bus hit overpass, injuring high school students: Police Two 17-year-old girls suffered serious injuries but are in "stable" condition.

Either the driver or a chaperone yelled "duck" before a charter bus carrying mostly high school students struck an overpass in Long Island, New York, state police said today.

The top of the bus was sheared off from the impact of the crash, which injured dozens of students. The bus was carrying high school students and traveling eastbound on the Southern State Parkway in Lakeview Sunday evening when it slammed into the overpass, police said.

Commercial vehicles such as buses are not allowed on New York state parkways because the bridges are so low in certain areas.

Two 17-year-old girls suffered serious injuries and are hospitalized in "stable" condition, police said.

They are expected to be discharged in 24 to 48 hours, the hospital said.

The various injuries ranged from broken bones to cuts and scrapes, New York State Police Maj. David Candelaria said.

Besides the two girls, five people suffered moderate injuries while the remainder were minor, police said in a news release.

"I think the entire incident could have been a whole lot worse," Dr. Joshua Kugler, South Nassau Communities Hospital director of emergency services, told ABC New York City station WABC.

The hospital’s emergency room doctors expressed surprise that everyone survived the crash, authorities said.

"Fate has a lot to do with it," Kugler told WABC. "People, if they were standing on the bus at any particular time and someone became an airborne projectile, could have had a different outcome."

Forty-four people were aboard the bus: the driver, five adult chaperones and 38 students.

"Everybody was able to walk out except one, which we extricated," Lakeview Fire Department Chief Patrick McNeill said, according to WABC. "There was glass everywhere. The roof of the bus is down to the top of the seat covers."

The teens, all between ages 16 and 18, were returning from John F. Kennedy Airport after a trip to Europe and heading to meet their parents at a nearby mall when the accident happened, authorities said.

“This was treated as a mass-casualty incident,” Candelaria, the state police major, said at a news conference at the scene. “I give credit the Nassau County police ambulance bureau’s emergency services unit and the Lakeview Volunteer Fire Department. They set up a mass-casualty treatment triage and probably saved lives.

“We’re very lucky. This could have been tragic," he added.

The bus was operated by New Jersey-based Journey Bus Lines and, in a statement, the company told WABC, said, "We're not making any comments at the moment. Our greatest concern is for is for the passengers and their families."

Police said the driver was unaware of the parkway system and the lower overpasses, adding there were no calls warning them about the presence of the bus on a road where it should not have been.

The driver was using a non-commercially issued GPS device and state police still need to verify the actual route through a forensic analysis of the device and passenger interviews.

The driver did have a commercial vehicle driver's license, police said.

"I don't think he had any awareness because if you look at the damage, it's a high-impact strike," Candelaria said.

The bridge is one of the lowest, if not the lowest, on the entire system, according to WABC.

Every on-ramp to the Southern State has a warning sign about the clearance restrictions, police said.

The New York State Police Department said Gaston had a blood-alcohol level of zero and a drug evaluation is still pending.

This was not a school-sanctioned field trip, WABC reported.

Many of the high school students in the area attend Huntington High School, according to the list of victims released by police.

"While injuries apparently ranged in severity, preliminary reports indicate that all have been treated and released, or remain under treatment,” Huntington Union Free School District Superintendent James Polansky said in a statement to WABC. “Our thoughts and prayers remain with all families involved. Student support staff remain on hand at Huntington High School for those in need.”

The students traveled to Eastern Europe through Education First, a tour company that sells and coordinates travel tours for students and educators, the company confirmed in a statement regarding the bus crash.

"All of us are shocked and saddened by the serious bus accident that occurred on Southern State Parkway in New York last night; our thoughts are with those who were injured. The tour had just returned from Europe and was traveling on a chartered bus to an arranged pickup point at the time of the accident," a spokesman for Education First told ABC News. "We are doing everything we can to support the students, chaperones, and their families. We are also working with public safety officials as they conduct their investigation."

Education First also said it is conducting its own review.

The crash is under investigation by state police.

The crash does not meet the criteria for a response from the National Transportation Safety Board but the agency is monitoring the case.

ABC News' Darren Reynolds contributed to this report.