(CNN) -- More than 20 people were injured when a jetliner headed to California hit severe turbulence and landed in Colorado on Tuesday night, authorities said.
United Airlines Flight 967 was en route from Washington Dulles International Airport to Los Angeles International, the Federal Aviation Administration said.
The Boeing 777 was diverted to Denver and landed about 7:30 p.m. (9:30 p.m. ET).
Twenty-one people were transported to local hospitals, said Scott Bookman, chief paramedic of Denver Health. He said they did not anticipate any more patients, but crews were on stand by. The Denver Fire Department earlier said that one person was seriously injured. Bookman did not comment on specific injuries.
"It's really unusual to see this many patients from a single episode of turbulence," he said.
Most of the casualties included moderate head, neck and back injuries, according to the chief paramedic.
"It seems like they got jostled around pretty good," he said.
Initial reports from the Denver Fire Department had put the number of injured at 30.
United said the plane had 255 passengers and a 10-member crew.
The airline will conduct an investigation, spokeswoman Megan McCarthy said.
Inspectors were en route to the airport, the FAA said.