An eighth-grade student and an adult were critically injured Monday when the bus they were riding from Philadelphia to Washington was clipped by a passing car on Interstate 95 in Harford County and overturned on the highway.

The collision sent the charter bus — carrying 26 students, two teachers and a parent on a class trip from the Charles W. Henry School in Philadelphia — veering off the highway. It struck an embankment and a tree before landing on its left side north of the Havre de Grace exit shortly before 9:30 a.m., Maryland State Police said.

One child was airlifted to Nemours duPont Hospital in Delaware and a woman was flown to Maryland Shock Trauma Center in Baltimore. Other passengers were taken by ambulance to area hospitals with lesser injuries.

Interstate 95 — which carries some 85,000 vehicles a day through the area — was closed in both directions for hours as first responders tended to the injured. Traffic backed up for miles in both directions.

The crash rattled students and weighed heavily on the paramedics tending to them, said Peter Quackenbush, chief of the Havre de Grace Ambulance Corps. Students with the least serious injuries were ushered to the side of the road to shield their view of the others, he said.

“It’s overwhelming,” Quackenbush said. “Your mind’s going 100 miles a minute, but you take a step back, look, and your training takes over and you prioritize.”

Drivers on the interstate and nearby were stunned by the scene: children sitting on the side of the road and others being put in ambulances.

Taxi driver Frank Drolet, 56, had just dropped off a rider on nearby Earlton Road and was heading south on Route 155 when lights and sirens filled his rear-view mirror. He said he pulled over and filmed a video on his phone from an overpass overlooking the scene.

“It was heart-wrenching,” he said. “I was praying the whole time. I’m still thinking about it. The damage can be fixed; I just hope the people are OK.”

Robin Roberts, a member of the Charles W. Henry School’s advisory council, said news of the crash sent panicked parents scrambling for information. Some got in their cars and headed to Maryland to be with their children, she said.

“These are kids I’ve known from when they were in kindergarten, and now they’re about to graduate,” she said. “Now graduation will be kids in slings and with broken bones.”

The trip is a familiar rite of spring for many eighth-grade classes, particularly on the East Coast. The students had left their school at 7:30 a.m. for Washington, where they were slated to visit the Lincoln and Martin Luther King memorials and the Newseum, said Kevin Geary, a spokesman for the Philadelphia School District.

Coincidentally, a bus filled with Philadelphia police recruits heading to Washington for Police Week was traveling behind the students’ bus. The recruits were able to help the injured off the bus, said Sgt. DaVaughn Parker, a Maryland State Police spokesperson.

“They were actually the first on scene,” he said.

The cadets were a “wonderful, wonderful help,” and had gotten everyone off the bus by the time the first responders arrived, Quackenbush said.

At the University of Maryland Upper Chesapeake Harford Memorial Hospital in Havre de Grace, emergency physician Dr. Steven Fountain said 17 victims of the crash were brought to his hospital with “contusions, sprains, minor lacerations.” He expected all would be discharged by the end of the day.

The patients included a teacher, whom Fountain described as more concerned about the students than herown injuries and making sure everyone was accounted for.

Nine passengers were taken to University of Maryland Upper Chesapeake Medical Center in Bel Air, suffering similar injuries, Fountain said, and all but two had been released by the afternoon.

Most of the injured at his hospital were “in good spirits … but obviously very worried,” he said. Most of the students had been reunited with parents who arrived at the hospital.

“It was quite a group effort,” he said of the response. “Everyone did a good job.”

Students asked if they’d have to go to school today, Fountain said.

Other bus passengers were taken to Christiana Hospital in Delaware.

Parker said the crash, near mile marker 88.9, remains under investigation but there is “no sign” the bus driver is at fault.

The driver of a blue, two-door Honda Civic had tried to pass the bus, which was in the middle lane, by moving into the fast lane, police said. There, he lost control of the vehicle, driving off to the left then returning onto the highway, crossing all three lanes of traffic and clipping the front of the bus, police said.

The driver of the Honda, whose name was not released, refused medical treatment, police said.

Parker said after completing the investigation, crash investigators will present their findings to the Harford County state’s attorney’s office to determine whether charges will be filed.

The chartered bus was operated by Werner Coach, a Pennsylvania-based company operating charters throughout the region. A spokesperson said shortly after the crash that the company was “still compiling” information from the scene. Later in the day, officials did not return calls for comment.

Werner Bus Lines, doing business as Werner Coach, earned a satisfactory rating from the Federal Motor Carrier Safety Administration in 2015, the year of its last rating. According to the federal safety records, the carrier has been involved in two crashes, one on I-95 in Delaware in February and another in Pennsylvania in October. Neither involved injures, but the buses needed to be towed away.

The company owns 24 buses and three mini-buses. It employs 38 drivers and drives more than 2 million miles a year, according to federal safety records.

It has been cited for 61 violations in 58 inspections over the past two years, mostly for maintenance issues, but including a handful of driver violations, ranging from using a mobile device while driving and exceeding the 10-hour driving limit.

Traffic from Monday’s accidentaffected some businesses in the area. Barber Kelly Hutchinson said her boss at Great Clips near Route 22 in Aberdeen sent her home early because so few customers were able to get to the salon. “It was the only thing people were talking about,” she said.

Z. Andrew Farkas, director and professor of the University of Maryland’s National Transportation Center, said, “Any shutdown of I-95 north of Baltimore will have a dramatic impact on personal and commercial traffic, because it is the East Coast’s Main Street.”

Baltimore Sun reporter Lorraine Mirabella and Baltimore Sun Media Group reporters David Anderson and Erika Butler contributed to this article.