(KLZA)--Columbus, Neb. – An issue with a siren caused it to sound off at approximately 8 a.m. Thursday morning near Rock Port, Missouri, just east of Cooper Nuclear Station. According to Nebraska Public Power District officials, this was a false activation of the siren believed to be caused by an internal malfunction in that specific siren. There was no problem at the plant that would have required activation of the siren, and at no time was there a threat to residents of the area around Cooper Nuclear Station. The cause of the false activation is being ascertained.