About 45 people were on the bus, the sheriff said.
The accident happened around 5:30 a.m. CDT (1030 GMT) on Interstate 10 between Mobile, Alabama, and Pensacola, Florida, Lowery said. WKRG-TV reported around 40 people suffered injuries - five of which were serious.
Several hospitals were placed on alert for the injured.
"We have one confirmed fatality", he said.
Texas high school students injured in Disney trip bus plunge
Mack said the bus was lying on its side, about 50 feet down the ravine.
At least 37 people, a lot of them teenagers, were treated at hospitals or other facilities in Pensacola and southwest Alabama for injuries that ranged from minor to very serious, medical officials said.
Some were rescued by firefighters, and others were carried out by deputies, Mack said.
Baldwin County Sheriff's Office Major Anthony Lowery said the bus plunged off Interstate 10 into a deep ravine Tuesday morning, and multiple helicopters are responding.More news: Trump's Personal Assistant Fired Over Security Issue
Channelview Independent School District spokesman Mark Kramer confirmed that the students are band members from Channelview High School.
At least one helicopter landed at USA Medical Center in Mobile, about 7 a.m.
One injured passenger taken to Baptist Hospital in Pensacola was in good condition.
Officials said the Baldwin County Emergency Management Agency facility in Robertsdale, Alabama, would be used as a staging area to reunite non-injured passengers with families. The rest of the injured, including a Baldwin County deputy hurt during the extrication process, suffered minor wounds, he said. They were going home to Channelview, Texas, a community about 15 miles from Houston.More news: HBO is throwing everything into Game of Thrones spinoffs
The Baldwin County call center is being brought online to field calls regarding the passengers and their locations, according to the Sheriff's Office.
Six or seven Medevac helicopters transported patients to hospitals, the sheriff said. We are in contact with law enforcement in Alabama trying to obtain further information.
Mack said it was expected I-10 would remain shut down at least until noon.
First Class Tours, which operated the bus, said in a statement that the bus was carrying students home from Orlando, Florida, and the company is cooperating with investigators.More news: Bears expected to retain top 3 RFAs with $1.9M tenders
This story is developing and will be updated.
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