The Taranaki District Health Board is investigating claims that the Department of Conservation showered its own workers with 1080 poison during an aerial drop.

DOC sub-contractors told One News they saw a helicopter spraying weeds in Egmont National Park, which dropped 1080 pellets on top of them.

Dan Beattie said that after their 12-strong crew left the area, the chopper returned and "dumped a whole lot more 1080 on us".

He said they were not phoned or warned about the drop until after it took place.

DOC said it had no obligation to warn the contractors.

Spokesman Phil Fleury said they had been told two days in advance that the poison could be spread dependent on the weather.

"The courtesy call is the 48 hours notice and the choice that they can make to be in there or not. We don't consider people were at risk while they were in the park while this operation was on."