how to explain this strange amplification chart? - the Ct value comes to be very low because of the unusual amplification (Sep/11/2007 )

Hi, all
I have run real time PCR for many times, it was the first time when I found out the Ct value tuned out to be as low as 1.17~3.0.I know that was not because of the high amount of the templete ,because the amplification chart was very strange ,after that this kind of situation happened several times ,I don't know understand why, so could anyone help me to find out the reasons?
Thanks!

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