Concerning message found on United Airlines plane forces flight to return to Hawaii

SUGGESTED: Plane makes emergency landing at LAX

SUGGESTED: A Qantas Airlines flight made an emergency landing at LAX after experiencing mechanical issues.

LOS ANGELES - A federal investigation is underway after a security issue forced a flight bound for Los Angeles from Honolulu to return to Hawaii overnight. 

What they're saying:

"United Airlines Flight 1169 returned to Daniel K. Inouye International Airport in Honolulu around 1:35 a.m. local time on Wednesday, May 21, due to a security issue. The flight was headed to Los Angeles International Airport. Contact the airline and local authorities for additional information," the Federal Aviation Administration (FAA) said in a statement. 

United also released a statement to FOX 11 that said, "United flight 1169 from Honolulu to Los Angeles returned safely to Honolulu after a potential security concern was found written on a lavatory mirror. Law enforcement met the aircraft, and a security sweep was conducted. We are rebooking customers on another flight to Los Angeles that departs later this evening."

The Boeing 777 had 339 passengers and 10 crew members. 

No further information was provided by officials.