A woman and her son were arrested from inside a train after US Dollar 1,38,700 in cash was seized from them at New Jalpaiguri railway station, a senior customs official said on Tuesday.
Acting on a tip-off, customs sleuths raided a general compartment of the Kanchanjunga Express when it reached New Jalpaiguri station on Monday.
The unaccounted cash was recovered from the possession of the woman and her son who are from Mizoram.
"Initial probe revealed that the two are involved in smuggling gold from Myanmar to Kolkata. It appears that they were returning after selling smuggled gold in Kolkata and getting the money," the customs official said.
After reaching Mizoram, they are supposed to send the money to Myanmar, he said adding that the two are being questioned.