Federal investigators promised a thorough investigation into what caused a charter bus carrying a high school marching band to veer off a New York highway in a wreck that killed two adults and seriously injured other passengers.

“Our goal is to find out what happened, why it happened, and to make safety recommendations to reduce the chance that this sort of accident never happens again,” National Transportation Safety Board investigator John Humm said at a press briefing Friday in Middletown, New York.

The charter bus, one of six carrying students from Farmingdale High School, was about 30 minutes from its destination at a band camp in Pennsylvania when it crashed on Interstate 84 in the town of Wawayanda, about 45 miles (72 kilometers) northwest of New York City.

The two adults who died were band director Gina Pellettiere, 43, of Massapequa, and Beatrice Ferrari, 77, of Farmingdale, a retired teacher who was serving as a chaperone on the trip.

Eighteen people -- 16 students and two adults -- remained hospitalized as of midday Friday, according to Bruce Blakeman, the county executive of Nassau County, where Farmingdale High is located.

In the next five to seven days, Humm said NTSB investigators will look into any mechanical issues with the bus, including its tires. New York Gov. Kathy Hochul said on Thursday that tire failure may have been to blame for the bus going off the road.

“It’s really premature at this point just to say, boom, it was the tire, that’s what caused it,” Humm said.

Investigators will also be looking into the Long Island-based operator of the charter bus, Regency Transportation, and its drivers, to see how they comply with federal regulations. Humm said investigators have not yet spoken to the female driver of the bus, but that they plan to.

Representatives of the company have not responded to requests for comment.

Ferrari had taught in the Farmingdale school district for more than 30 years before retiring. Pellettiere taught music for close to two decades.

Pellettiere “absolutely loved what she did,” Jason Giachetti, who worked with her at a previous job, told Newsday, “and the kids loved her.”

Cordelia Anthony, a science teacher at the high school, said Ferrari was a “wonderful history teacher” and had chaperoned the band for years.

The school was open Friday with counselors available to grieving students and staff members.

The buses were taking the marching band, color guard and dancers from Farmingdale High on an annual trip a band camp in Greeley, in northeastern Pennsylvania.

Student Anthony Eugenio, 15, was asleep on the bus Thursday when he was jarred awake to find it tipping over. He said he was able to crawl out of the bus through a window with just scrapes and bruises, but that other students were bloodied.

State police officials were asking the public on Friday for any dash camera videos that may have recorded the incident.