Three-dozen bus drivers for a city summer program were injured early Thursday after the bus they were riding in flipped onto its side on a Bronx highway, police said.

The yellow school bus — which had no children aboard — was heading north on the Hutchinson River Parkway after passing the Cross Bronx Expressway interchange around 5:55 a.m. when it overturned as it took exit 1A, cops said.

The bus ended up on its side on the exit ramp, police said.

The passengers were all school bus drivers for the city’s Summer Rising program, Mayor Adams said in a statement.

“The safety of every member of our community is our top priority and thankfully, at this time, no major injuries have been sustained on board,” Adams said, adding that the accident would undoubtedly lead to delays for summer programming bus routes Thursday morning and afternoon.

Three people suffered serious, but not life-threatening, injuries and were taken to area hospitals, an FDNY spokesman said.

The remainder suffered minor injuries, the FDNY said.

Police were investigating what caused the crash.

The school bus is owned by Consolidated Bus Transit Inc., which has been involved in 30 crashes over the past two years, according to the Federal Motor Carrier Safety Administration.

The company, located in Brooklyn and the Bronx, has a fleet of more than 1,000 vehicles and 952 drivers, the website noted.

Company spokeswoman Caroline Daley said the bus was transporting workers from the Brooklyn facility to the Bronx facility.

“Right now we’re investigating the cause of the crash with police authorities,” Daley said. “Our immediate concern is the safety and well being of our employees.”

Summer Rising is a free academic and enrichment program for city grade school students.

Parents wanting to know if their Summer Rising bus routes will be delayed because of the accident can call the Department of Education’s Office of Pupil Transportation call center at (718) 392-8855.