An organisation opposed to the use of methyl bromide claims Picton residents have again been put at risk by the fumigation of logs.
The Soil and Health Association says tons of the gas were released on Monday night when logs in the hold of a 170-metre ship, the Pontonostos, were fumigated in Shakespeare Bay.
It says stacks of logs on the wharfside were also fumigated.
Port Marlborough has confirmed the work took place on the ship and 17 stacks of logs were fumigated.
The association and the Guardians of the Sounds fear light north-westerly wind prevalent at the time would have carried the gas over Picton. They are concerned about the cumulative effects of the fumigations.
Methyl bromide has been blamed for the deaths of five Port Nelson workers, although a medical inquiry dismissed the connection.