State Police representative Andrejs Siņavins said the quantity seized was more than four times the usual yearly average.
It was worth around €600,000 on the black market, and the illegal substance had been made for selling in Northern European countries.
The lab, located at an unused private house, had been operational for about two months.
Three people were arrested with one kept behind bars in an operation that also involves people abroad, with foreign police on the lookout for the other criminals involved in the scheme.
