The four hailing from Chennai, were arrested based on a tip-off, they said.
Preliminary investigations revealed that the gang had arrived in Karaikudi yesterday and had contacted one Ganesh Udayar to change the old currencies, but in vain.
They were instructed by a man from Chennai to hand over the amount to the correspondent of a private engineering college in the district.
Further investigation is on. Police said the central government officials also had been informed of the seizure.
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