SAN FRANCISCO (CBS SF/AP) — A engine seal failed on a Hawaiian Airlines flight from Oakland to Honolulu, causing oil to leak onto hot parts of the plane’s engine and air conditioning system, resulting in smoke in the cabin, airline officials said late Thursday.

The smoke triggered an emergency landing and evacuation on the tarmac. Seven passengers were transported to local hospitals due to smoke-related symptoms.

“The performance of the engine was not affected, and the Airbus A321neo flight landed without incident,” the company said in a statement.

Meanwhile, shuttles took the other passengers to a staging area at the airport where they were able to pick up their luggage.

Jon Snook, Hawaiian Airlines chief operating officer, said smoke was first detected on Hawaiian Airlines Flight 47 about 20 minutes prior to landing as the plane began to descend.

American Medical Response spokesman James Ireland said a total of 11 patients had breathing complaints and seven were taken to the hospital with respiratory problems.

Ireland said the youngest patient taken to the hospital was a 9-month-old. He said another older child was also taken to the hospital and the rest were adults. All injuries were considered minor.

One person was examined at the scene for injuries sustained during the evacuation.

Snook said there was visible smoke in the cabin and a smoke indication in the cargo hold set off a warning in the cockpit, which prompted the emergency landing. He said there were no visible flames anywhere on the plane.

An automatic fire suppression system was activated in the cargo hold, Snook said.

He said smoke was still prevalent in the cabin after the plane landed, which is why the passengers were ordered to use the slides to evacuate the aircraft.

Snook thanked the crew and passengers for evacuating in an orderly way “in what could have been a complex and dangerous situation.”

Snook said the National Transportation Safety Board will be notified and conduct an investigation. The Federal Aviation Administration will also investigate, said spokesman Allen Kenitzer.

Firefighters said it took the passengers just 30 to 45 seconds to exit the aircraft. A few had only minor bruises from coming down the slides, said Glenn Mitchell, the airport’s fire chief.

© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.