TOKYO (AP) - Japanese public broadcaster NHK says its erroneous alert of a North Korean missile fired at Japan was sent by a staff member who meant to file a different news flash.
    
NHK denied any mechanical flaw and said Wednesday it is studying preventive measures.
    
The erroneous news flash Tuesday said North Korea appeared to have fired a missile at Japan and that the government was warning people to take shelter. NHK retracted the mistake within minutes and apologized on air and on other formats.
    
NHK isn't sure how many of its 300,000 social media followers saw the alert or notification and it's unknown if anyone followed the instructions.
    
Days earlier, Hawaii's emergency authorities sent a mistaken warning of a missile attack to mobile phones across the state, triggering panic.

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