For 38 harrowing minutes, residents and tourists in Hawaii were left to believe that missiles were streaming across the sky toward the Pacific island chain after an erroneous alert yesterday by the state's emergency management agency.

"Ballistic missile threat inbound to Hawaii," warned an 8.07am (7.07am NZT) message transmitted across the state's cellphone networks. "Seek immediate shelter. This is not a drill."

Only after an inexplicable delay by the state agency - during which residents scrambled to seek shelter and contact relatives - was a subsequent message sent describing the missile warning as a "false alarm".

The frightening mistake, which Governor David Ige later attributed to a state employee's errant push of a button, prompted outrage and calls for an investigation into how such an error could occur and take so long to correct.

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The episode underscored the already heightened level of anxiety at the western edge of the United States amid mounting tensions with North Korea over its nuclear arsenal and the menacing social media exchanges between US President Donald Trump and its leader, Kim Jong Un.

On the island of Oahu, Adam Kurtz of Palolo woke up four minutes after the mass alert was sent and began calculating how much time he and his wife might have to get to safety - assuming there could be no more than 15 minutes between the warning and any missile's arrival.

Kurtz said that he and his wife grabbed the pets, shut the windows and sheltered in their bathroom. "We just jumped out of bed. We were more clearheaded than we expected and didn't panic as much," said Kurtz, who learned that the alert was false from a friend who contacted state Department of Defence officials.

Ige said the false warning was "a mistake made during a standard procedure at the changeover of a shift and an employee pushed the wrong button". At a later news conference, Ige and Hawaii Emergency Management Agency Administrator Vern Miyagi promised that no single person will be able to cause such an error in the future.

Miyagi said a rule has already been put in place to mandate that two people be present before the button is pushed to alert for a drill or emergency. He also said a cancellation message template will be created for such an error scenario so a delay like yesterday's does not happen again.

Diamond Head, an extinct volcanic crater, and high-rises are seen in Honolulu. Photo / AP
Diamond Head, an extinct volcanic crater, and high-rises are seen in Honolulu. Photo / AP

But the explanation on how the alert was sent came only after concern over the mistaken missile warning had spread to US military command posts and been brought to the attention of Trump, who was spending the weekend at his Mar-a-Lago estate in Florida.

The false alert prompted US military officials to scan systems that monitor missile launches; they determined almost instantly that there was no threat. But officials described confusion over whether or how the military should correct a state-issued alert.

At the North American Aerospace Defence Command, which tracks the skies for threats to the US, troops manning the watch floor confirmed within minutes that there were no missiles bearing down on Hawaii. That information was quickly relayed to state officials, said Navy Lieutenant Commander Joe Nawrocki, a spokesman for the command.

But Hawaii struggled to issue a comprehensive correction. The Hawaii Emergency Management Agency transmitted its first "no missile threat" message within 12 minutes of the mistaken alert, but that revision only went out on the agency's Twitter account.

It wasn't until 8:45am that the agency was able to issue a stand-down message across the same cellphone and cable television networks that had spread the initial, erroneous warning. By that time, officials from Hawaii including Congressman Tulsi Gabbard had taken it upon themselves to distribute stand-down messages on social media.

"What happened today is totally inexcusable," Senator Brian Schatz said on Twitter. "The whole state was terrified. There needs to be tough and quick accountability and a fixed process."

Deputy White House press secretary Lindsay Walters said Trump had been briefed. A senior US official said Trump was at the golf course at Mar-a-Lago when the alarm was sounded and knew "soon after" that it had been determined false.

In the hours after the false alert, images and postings on social media showed people flooding highways, crowding into police stations and seeking shelter in concrete structures including parking garages. One post on Twitter showed a resident lowering children through a manhole in a footpath.

Tricia Padilla, 39, of Kauai, her husband and their two children, aged 10 and 12, hid in a steel shipping container on their lawn. "We just flew into full on mum-and-dad mode and tried to protect our kids from the panic of it," she said. They took with them cereal, protein bars, cookies, apples, turkey, water, a bucket to use as a toilet and toilet paper.

"My 10-year-old was kind of melting, sitting at my feet rocking, saying, 'Mum, are we going to die today? Why won't you answer me?' And I wanted to answer him but I couldn't. It felt like my worst mum moment," Padilla said.

Toni Foshee, a resident of Palolo, said she and a friend visiting from California reacted as if a hurricane were coming - making sure her cat was indoors, shutting windows and waiting. "I think I was just kind of numb," she said, adding that they learned the alert was false after calling the police.

US military personnel stationed in Hawaii described moments of near desperation.

One Navy sailor, speaking on the condition of anonymity because he was not authorised to talk to reporters, said that he awoke yesterday in Honolulu to his girlfriend asking him about the alert.

Shocked, he turned on the television looking for more information and called his mother in Massachusetts to let her know what had happened and say he loved her.

The sailor eventually called the Honolulu Police Department about 10 minutes later, and the dispatcher told him that the alert was a mistake.

"How can that happen?" he said of the error. "How can you allow to that to happen? There's just an anger that goes with it. Even now, I'm shaken that it happened. You go from thinking you might die to this. It's just a weird feeling."

Because of its mid-Pacific location, Hawaii has long confronted the possibility that it would be the target of any North Korean attack on the United States. That worry has intensified in recent months amid escalating signs of conflict between Pyongyang and Washington.