They were walking out on the track between Whangamumu and the Rawhiti Rd when the helicopter flew over them and dropped a load of pellets, the post said.
DoC Bay of Islands operations manager Rolien Elliot said the department is investigating the claim.
''There was some innuendo the helicopter pilot deliberately dropped pellets on them,'' Elliot said.
''I sincerely doubt if that was the case, but it needs to be investigated.
''It is our job to make sure the whole operation is safe for the public as well as our staff and contractors.
''However, the men knew the operation was happening, they chose to go in there.''
Elliot said she understood the group of about six hunters with some dogs had arrived at Whangamumu around 12.30am on Saturday morning, crossing private land as public access via a DoC track was closed due to the 1080 drop.
They were fishing at first light when a hapu representative working alongside DoC in a liaison role asked them to leave because the operation had started, she said.
The man then followed the group out on DoC's Whangamumu to Rawhiti Rd track.
He called the operation's incident controller immediately to report they were in the drop zone and pellets had fallen around them, Elliot said.
The person who made the social media post was unwilling to talk to the Northern Advocate about it.
Meanwhile, photos of the eel, pellets in streams and dead possums have gone viral. DoC said people who find dead eels and are concerned about why they died can take them to a DoC office to be tested for 1080.
The Russell State Forest and Cape Brett 1080 programme will be followed up with water sampling, carcass and hapu-led environmental monitoring.
''I'm hoping the results of the operation and future monitoring will help show the benefits of the 1080 operation,'' Elliot said.
DoC has reiterated research showing the poison's rapid water-solubility to harmless concentrations.
Forest and Bird has cited post-1080 tests showing that of 3701 samples from drinking water supplies and natural waterways over 20 years, Landcare Research found only five contained traces of 1080.
All five were less than two parts per billion, well below the Ministry of Health's guidelines for drinking.