A New Zealand stevedoring company is to start blood testing workers for traces of methyl bromide following claims that former port workers contracted fatal diseases from the gas while treating timber.

The move by Stevedoring Services Nelson (SSN) at Port Nelson comes as pressure mounts for an official inquiry into the deaths of five men who contracted motor neurone disease after years of working at the port.

Methyl bromide is used to kill pests before timber is exported to Australia. The port’s medical officer, who is examining the cases, has admitted that exposure to the gas could cause sickness, including neurological symptoms.

SSN will also carry out tests on vessels to monitor any leaching from fumigated timber loaded at other ports.

Port Nelson said blood tests had been carried out for several years on six workers involved with fumigation without any abnormal readings being reported.