A missile alert sparked panic among residents of Hawaii on January 13 before it was declared to be false.
Mobile phone users received a message saying: “Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill.”
Hawaii Governor David Ige apologized to people, saying an employee had pressed the wrong button.
Meanwhile, the US government announced there would be a full investigation.
An alert system is in place because of the potential proximity of Hawaii to North Korean missiles.
Last month, Hawaii tested its nuclear warning siren for the first time since the end of the Cold War.
According to the Associated Press, a push alert was sent to people’s phones.
The phone message, all in capital letters, went out at 08:07 local time.
The message was corrected by email 18 minutes later but there was no follow-up mobile text for 38 minutes, the Honolulu Star-Advertiser reports.
In a tweet, Hawaii’s Emergency Management Agency (EMA) said simply: “NO missile threat to Hawaii.”
TV and radio broadcasts across the state were also interrupted with a recorded emergency message: “Stay indoors!
“If you are outdoors seek immediate shelter in a building. Remain indoors well away from windows. If you are driving pull safely to the side of the road and seek shelter in a building while laying on the floor. We’ll announce when the threat has ended. This is not a drill!”
Matt Lopresti, a member of the Hawaiian House of Representatives, was at home when he received the emergency alert on his mobile phone.
He described how he and his family had sought shelter in a bath tub.
He told local broadcaster KGMB: “We got our children, grabbed our emergency supplies, put them in our most enclosed room in our house which is our bathroom.
“We put them in the bath tub, said our prayers, tried to find out what the Hell was going because we didn’t hear any alarms, any of the sirens.
“There’s not much else you can do in that situation. You know, we did what we could… and I am very angry right now because it shouldn’t be this easy to make such a big mistake.”
The US military confirmed no missile threat had been detected and the alert had been released in error.
Ajit Pai, chairman of the US Federal Communications Commission, announced an investigation.
He tweeted: “The @FCC is launching a full investigation into the false emergency alert that was sent to residents of Hawaii.”
North Korea’s missile and nuclear program is seen as a growing threat to America. Hawaii is one of the American states closest to North Korea.
In September, North Korea carried out its sixth nuclear test.
In December, the Star-Advertiser reported that a missile launched from North Korea could strike Hawaii within 20 minutes of launch.