The blaze was reported at 8:45 p.m. at the Regency Inn and Suites in the 14600 block of Dalewood Street, according to the Los Angeles County Fire Department.
Firefighters arrived to find smoke emanating from the fourth floor of the hotel after flames erupted in a single unit on the third floor, officials said.
The nine patients suffered minor smoke inhalation and were transported to hospitals for treatment.
Guests at a Baldwin Park Motel escape a fire on the 3rd floor. Some are treated for minor smoke inhalation. The story at 11pm. pic.twitter.com/ePMhDkJy3V— Melissa MacBride (@abc7melissa) February 20, 2017
A spokesperson for the fire department announced on Twitter that within 30 minutes the fire had been contained to the one room where it began.
Lucy Moreno was on the fourth floor at the time of the incident. She said there was so much smoke that she could not see as she made her way down a hallway.
"I don't know how I did it, to be honest, because I just saw pure black," she recalled. "I was just struggling. It was as if I was blind. ... I couldn't even see the stairs. When I opened the door, all the smoke just came in. It was a really bad experience."
The incident prompted a SigAlert on the nearby eastbound 10 Freeway, whose Puente Avenue offramp was closed while multiple police vehicles, fire engines and ambulances remained at the scene.
The cause of the incident was not immediately known.