Heroin worth one crore rupees was seized in Chennai on Sunday and seven persons arrested in this connection, police said.
Acting on a tip-off, police stopped a car near Perambur in the city, seized the contraband and arrested the driver.
Six others were taken into custody from different places in the city based on information given by the driver during questioning, the police said.
One of the arrested were identified as Natrajan (44) working as a security guard in Cuddalore Port.
Preliminary investigation revealed that the heroin was meant to be smuggled to Singapore by a ship, they added.