The large, white bus was too tall for the 8-foot-6-inch entrance to the arrivals area, said airport spokesman Greg Chin. Buses are supposed to go through the departures area, which has a higher ceiling, he said.
Chin said passengers told him they were part of a group of Jehovah's Witnesses headed to West Palm Beach. Police said in a news release that the group had chartered the bus to take them to a church convention there.
The group was made up of congregation members of Sweetwater's Kingdom Hall of Jehovah's Witnesses, said Sweetwater Mayor Manny Maroño.
"This is a tragic accident that has affected many families, as well as, our Sweewater family," Maroño said in a press release. "I am pursuing all avenues to get in touch with the appropriate persons to officially extend our help to the congregation and those who were hurt."
A phone number listed for the center in Sweetwater went unanswered.
At the airport, two large signs warn drivers of large vehicles not to pass beneath the concrete overpass. One attached to the top of the concrete barrier reads: "High Vehicle STOP Turn Left." The other, placed to the left of the driveway and several feet in front of the barrier, says all vehicles higher than the 8-foot-6 threshold must turn left.
Three people were at hospitals in critical condition. The other 27 surviving passengers were hurt, but their injuries were less extensive, authorities said.
One person died at the scene; the second died later at a hospital. Police said it was not immediately known if charges would be filed.
Osvaldo Lopez, an officer with the Miami-Dade Aviation Department, said he first heard a loud noise Saturday morning and was certain it was some sort of car wreck.
He said he went inside the bus to help and found several passengers thrown into the center aisle. He said the passengers, many of whom were elderly, remained calm after the wreck.
"It was just very bloody," he said of the scene.
After helping the passengers, Lopez suffered some injuries of his own - his left arm and a finger on his right hand were both bandaged.
Fire trucks and police cars swarmed the area after 8 a.m. Saturday, and the bus was blocked off by yellow police tape. A white cooler that had been filled with water bottles was on its side behind the bus, the front of which remained wedged beneath the overpass for hours before it was towed away.
The bus was privately owned and typically used for tours, though police believe all the passengers were local residents, said Miami-Dade police Lt. Rosanna Cordero-Stutz. The driver was unfamiliar with the area near the airport and did not intend to wind up at the arrivals area, Cordero-Stutz said. Investigators were interviewing the driver, she said.
The bus was going about 20 mph when it struck the overpass Saturday morning, Chin said.
The bus model is commonly used for charters and tours, with the driver seated low to the ground and passenger seats in an elevated area behind the driver's seat.
Markings on the bus show it was owned by Miami Bus Service Corp.
Federal Motor Carrier Safety Administration records found online show the company has had no violations for unsafe driving or controlled substances and alcohol. It also had not reported any crashes in the two years before Oct. 26, 2012.
The records show it did receive three citations related to driver fatigue in April 2011.
The company owns three motorcoaches, according to the records. Miami Bus Service Corp. officials did not immediately respond to a phone message Saturday.