A man and his son were arrested with 1.9 kg heroin in Mizoram's Hnahthial district near the Myanmar border, the police said on Sunday.
The heroin, worth around Rs 1.55 crore in the local market, was smuggled from Myanmar, they said.
Duhkima (62) and his son Remthangpuia (33) were arrested with the drugs on Friday night from Ngharchhip village, the police said.
They also dropped about Rs 280 grams of heroin, worth Rs 15 lakh, while swimming across a river as they tried to flee from the police, officials said.
According to police, the seizure was believed to be the biggest heroin haul in the state.
The accused were charged under the relevant sections of the Narcotic Drugs & Psychotropic Substances (NDPS) Act, 1985.
Even as the inter-state borders and the one with Myanmar remained sealed in the wake of the coronavirus outbreak, smuggling of drugs and other contrabands continued unabated, the police sources said.
The Assam Rifles recently seized 25 trucks loaded with betel nuts, valued at Rs 4 crore, being smuggled from Myanmar, they said.