"He was captured at a post office while attempting to send another mail (containing poison) to Czech officials," police spokesman Miran Ozebek told Pop TV adding the Italian had been detained in the Nova Gorica area bordering Italy at the end of December.
He added that the envelope contained ampoules of an unidentified toxic substance, but did not give more details.
Two Czech ministers from the centre-left government in November received envelopes containing poison. One of them, addressed to Finance Minister Andrej Babis, had been sent from Slovenia, while the other, to Interior Minister Milan Chovanec, from Sweden, according to Czech media.
The Italian national allegedly sent the envelopes "because he does not agree with the Czech (government's) policy," Pop TV reported, quoting unnamed sources.