Two of the injured people were airlifted to Wellington Hospital.
They will be tested on emergency procedures if a train derails.
The crash happened on Friday evening.
Police said they did not believe there was an ongoing risk to the public.
It's understood the spill is at the ferry terminal.
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The vehicle rolled 200 metres down a hill in Marlborough.
Marlborough Girls' College and other nearby schools went into lockdown.
"These young adults will struggle to get back on their feet and live a normal life."