An investigation into the suspicious fire at Levin's Horizons Regional Council depot was stalled for a month due to hazardous substances.
The January fire damaged property, equipment and vehicles stored at the depot.
It was confirmed by police that the depot had been broken into and a quad bike set alight.
Controversial pest control poison 1080 was stored at the depot along with herbicides for weeds, cyanide and rabbit toxins.
Horizons chief executive Michael McCartney confirmed that a 1080 casing was damaged in the fire.
Waste Management Technical Services recently removed and disposed of the hazardous substances, allowing Police to do an internal scene examination on Tuesday.
Mr McCartney said the removal was a complex and time-consuming task but it was now completed and all poisons accounted for.
He said the hazardous substances were not removed immediately following the fire to ensure their casings did not break.
"We did not want to risk moving them until we could ensure this could be done without risk to the environment or human health."
Mr McCartney says the site has been under 24-hour security since the fire occurred and will remain closed to staff and the public until further notice.
Detective constable Michael O'Hagan said he was finally able to do the first police internal scene examination on Tuesday.
Initially police believed items had been taken from the depot on the night of the fire.
However, Detective O'Hagan said they now believe nothing was taken. Police will be putting all evidence together to look at new avenues of enquiry.