Across Hawaii, residents got an ominous message on their phones’ Emergency Alert System (EAS) telling them to “seek immediate shelter” from a “ballistic missile threat.”

Multiple officials and government agencies quickly confirmed the message was a false alarm:

HAWAII – THIS IS A FALSE ALARM. THERE IS NO INCOMING MISSILE TO HAWAII. I HAVE CONFIRMED WITH OFFICIALS THERE IS NO INCOMING MISSILE. pic.twitter.com/DxfTXIDOQs — Tulsi Gabbard (@TulsiGabbard) January 13, 2018

NO missile threat to Hawaii. — Hawaii EMA (@Hawaii_EMA) January 13, 2018

U.S. Pacific Command has detected no ballistic missile threat to #Hawaii. Earlier message was sent in error and was a false alarm. pic.twitter.com/Lvg17VNjiF — U.S. Indo-Pacific Command (@INDOPACOM) January 13, 2018

White House Deputy Press Secretary Lindsay Walters later implied the false warning stemmed from a state, rather than federal, mishap. “The President has been briefed on the state of Hawaii’s emergency management exercise. This was purely a state exercise,” he said in a statement

According to the Associated Press (AP), Hawaii Emergency Management Agency spokesman Richard Repoza confirmed a false alarm.

“Hawaii Emergency Management Agency spokesman Richard Repoza said it was a false alarm and the agency is trying to determine what happened.,” the AP reports.

The message, initially thought authentic, spread quickly on social media, prompting some panic, as Fox News reported Rep. Tulsi Gabbard (D-HI) estimated over one million Hawaiians received the erroneous alert. The EAS protocol should only be available to government officials.

.@TulsiGabbard: "Cell phones all across the state – over a million people in my home state of Hawaii – got this alert." https://t.co/qJu9Jmyz66 pic.twitter.com/OiGXUH3ZlM — Fox News (@FoxNews) January 13, 2018

The location of the false alarm, Hawaii, was particularly worrying as it is some of the closest American territory to nuclear pariah state North Korea, which now possesses ballistic missiles reportedly capable of reaching the Aloha State.

According to Fox News, around 35 minutes passed between the initial false warning and a follow-up EAS message retracting it:

Report: 35 minutes between missile alert and false alarm notification. #Hawaii pic.twitter.com/nf4XD1sed4 — Fox News (@FoxNews) January 13, 2018

That 35 minutes would be almost exactly the warning expected before impact if a North Korean ballistic missile were detected at the moment it was launched. In August, Business Insider quoted David Wright, a physicist with the anti-nuclear weapons group Union of Concerned Scientists, as estimating the total missile flight time at 37 minutes. Some early warning systems can sometimes detect pre-launch conditions, like rising heat at missile silos indicating the missile is being fueled, that can give longer warnings.

In November, the Hawaiian government reactivated cold war era missile warning sirens over concerns about North Korean bellicosity. That move followed months of efforts by Hawaiian officials to develop contingency plans for dealing with a North Korean attack. Some of that planning apparently included “a public information campaign.”

It is unclear if Saturday’s mishap was related to any of these increased precautions.