Dozens of people were seriously injured after a Hawaiian Airlines flight en route to Honolulu experienced severe turbulence, in what’s being called a “very rare” event, according to officials.

Hawaiian Airlines Flight 35 was flying from Phoenix Sky Harbor International Airport to Daniel K. Inouye International Airport in Honolulu when the pilots reported severe turbulence around 10:30 a.m. Hawaii Standard Time on Sunday, the Federal Aviation Administration said in a statement.

The Airbus A330 was about 30 minutes outside of Honolulu when it began experiencing turbulence, according to Honolulu EMS. The flight landed safely in Honolulu at about 10:50 a.m., according to a statement from Hawaiian Airlines.

Paramedics and emergency medical technicians who responded to the scene treated 36 patients, 20 of whom were transported to local hospitals, officials said. Eleven patients were initially listed as in serious condition, while nine were listed as in stable condition, according to officials.

The youngest patient treated was 14 months old, according to Honolulu EMS. Injuries included a serious head injury, lacerations, bruising and loss of consciousness.

This type of event is “very rare,” Honolulu EMS Director Jim Ireland said, adding that while authorities initially thought there were some patients with critical injuries, “after further assessment, it doesn’t look like that they’re that severely injured.”

There were 278 passengers and 10 crew members on board the flight, the airline said.

Additional information was not immediately available.

The FAA is investigating the incident, the agency said.

This is a developing story. Please check back for updates.

ABC News’ Marilyn Heck and Alex Stone contributed to this report.