"Police have evacuated residents down-wind to the rugby club and we [Fenz] are decontaminating the site with detergent."
A resident, who did not want to be named, said the chemical might have belonged to the man, now deceased, who previously lived at the property. He believed the man "most likely" used chloropicrin to help the maintenance of his collection of orchids and other plants in a glasshouse on the site.
It is understood the new owner of the site alerted emergency services when they discovered the leaking drum.
A Fenz spokesman confirmed chloropicrin was commonly employed as a pesticide, for fumigation.
Residents were allowed to return to their properties yesterday afternoon after a 300m exclusion zone had been imposed earlier in the day. Pupils at St Mary's School, which was earlier placed in lockdown, were later allowed back outside.
In a social media post, the Clutha District Council said police had evacuated houses in the vicinity and the council had opened the Toko Rugby Club at the AMP showgrounds in Milton for affected residents to use.
Fenz said no-one was injured during the incident.
- Jack Conroy