Six passengers, including a child, were treated at the scene for bumps, bruises and other minor injuries, city fire spokesman Brian Humphrey said.
American Airlines Flight 31 to Honolulu, carrying 188 passengers and six crew members, took off from LAX at 8:48 a.m., American spokesman Tim Smith said.
A short time later, the pilot decided to turn back.
"They had some type of smoke or odor in the cabin," Smith said.
The Boeing 757 returned about 57 minutes later and made a safe landing but "the captain elected to declare an emergency and get everybody out of the aircraft via the slides," Smith said.
Televised reports showed passengers stepping from two cabin doors and sliding down the inflatable chutes. Los Angeles firefighters in helmets and yellow turnout coats stood by at the bottom to help them up. Smith said some people left the plane using stairways rolled to the exits.
The firefighters, including crash rescue specialists, then used thermal imaging cameras to check for fire, Humphrey said.
"Firefighters scoured the entire cabin and cargo hold and thus far found no evidence of an active fire," Humphrey said.
He said the plane was taken to a maintenance facility where the airline, National Transportation and Safety Board and the Federal Aviation Administration will investigate.
The passengers were taken by airport buses to a terminal and will be placed on another plane to Hawaii, but it was unclear how long they would have to remain at the Los Angeles airport, Smith said.
The emergency landing delayed six airborne flights that were approaching the airport and five departures, FAA spokesman Ian Gregor said. Air traffic controllers also grounded several aircraft that were within a one-hour flying time of the Los Angeles airport, he said.
Gregor could not recall the last time an aircraft had to deploy evacuation chutes at the airport.
"You hear from time to time about planes returning to airports because an indicator light went on, but it's pretty rare that they actually deploy chutes," he said. "That's essentially up to the pilot, who makes the call based on the particular circumstance he or she faced."
Smith said one reason the pilot deployed the chutes was the aircraft was totally full of passengers.
"That's one of the ways to quickly evacuate everybody," he said.
The firefighters actually were preparing for a publicity event for a different aircraft. Fire trucks were supposed to release streams of water to welcome Emirates Airbus A380 -- the world's largest jetliner -- on a flight up the West Coast.
That plane landed safely within sight of the aborted American Airlines flight.
The emergency landing delayed the Emirates flight for about 45 minutes, and the water cannon ceremony was scrapped, said Erin Franklin, a publicist for the event.