LOS ANGELES (AP) — Los Angeles International Airport slowly returned to normal Monday after false reports of a shooter sent hundreds of panicked passengers racing onto streets or the tarmac and caused major flight delays, authorities said.

Officers with rifles stormed terminals but uncovered no evidence of a gunman or shots fired Sunday. Loud noises spurred the reports, and police were still investigating their source, Los Angeles police spokesman Andy Neiman said.

It’s similar to a false alarm that led to a panicked evacuation two weeks ago at Kennedy Airport in New York, when a boisterous celebration of the Olympics may have been misinterpreted as gunfire, authorities say.

The Los Angeles scare created a mess, with three terminals shut down, roads closed and flights held in the air and on the ground, but no reported injuries. About 280 flights were delayed, while at least 27 flights were diverted to other airports and two were canceled, airport spokeswoman Nancy Castles said.

Vehicle traffic was flowing again on the upper departure level during morning rush hour, but cars backed up on the lower arrival area, Castles said.

All terminals and roads into the airport reopened by 11 p.m. Sunday, about two hours after the initial reports, officials said. Besides traffic, travelers faced a massive backup in security lines because those who fled had to be rescreened through security. 

Airport officials said a person wearing a Zorro costume was detained during the chaos, but it wasn’t yet clear whether the person had any connection to the evacuation.

“We were on the jetway, and someone starts pushing behind us,” Jon Landis, a sales representative from Boston who was boarding a flight home, told The Associated Press. “One man was frantic, saying there was a shooter.”

Police officers, including one with a shotgun, eventually led passengers out of the terminal, through a security gate and into a parking lot, where several hundred people waited. Ninety minutes after the scare, Landis said he was still waiting for word on his flight.

Scott McDonald said he was getting off a plane in the middle of the chaos and the crew told him to get back on. Looking out the window, he said he could see many evacuees gathered on the tarmac, a strange sight even for someone who travels constantly.