Television broadcasts and mobile phones in Hawaii were interrupted by an emergency warning of an incoming missile on Saturday.
The emergency sent to mobile phones warned, in capital letters: “Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill.”
A video on social media showed the emergency system interrupting the broadcast of a football manage, with a high-pitched sound alerting viewers to their screens which displayed the same warning.
The message was accidentally sent at 8.07am local time (6.07pm GMT) and a retraction message was sent 38 minutes left.
According to Hawaii Emergency Management Agency spokesman Richard Repoza, the alert was sent in error.
Mr Repoza said the agency was trying to determine what happened.
The US military’s pacific command said that there was no ballistic missile threat to Hawaii.
A spokeswoman for US Representative Tulsi Gabbard said she checked with the state agency that issued the alert and was told it was sent in error.
Ms Gabbard then tweeted to Hawaii, in all-caps: “There is no incoming missile to Hawaii. I have confirmed with officials there is no incoming missile.”
Hawaiian Senator Brian Schatz said on Twitter: “There is no missile threat. It was a false alarm based on a human error.
“There is nothing more important to Hawaii than professionalizing and fool-proofing this process.”
“Again false alarm,” he wrote in all capitals.
“What happened today is totally inexcusable. The whole state was terrified. There needs to be tough and quick accountability and a fixed process.”
According to social media reports, the alert sent many of the islanders into a panic.
The message seems to have been sent as part of the US Wireless Emergency Alerts (WEA) system, which allows authorised national, state or local government authorities to send alerts regarding public safety emergencies.
Last December, the Pacific island tested sirens warning of an impending nuclear attack from North Korea.
Hawaii had been named as a potential target of an intercontinental ballistic missile launched by Kim Jong Un, who has threatened the US with a nuclear strike.
Officials in Hawaii have spent months briefing the public on what action to take in the event of an attack. It is estimated that Hawaiians would have less than 20 minutes before the missile arrived.