The first anomaly was detected by the Finnish defence forces in Kajaani already the previous day, Sunday evening at 8:40pm local time, but they didn't understand the small deviation was very important and probably suspected it was a minor error in the measurements. Only on Monday at 10am the Nuclear Safety Authority started to investigate properly and published information at 4pm - not early enough to let Forsmark know they wouldn't have needed to evacuate the plant as a precaution.