The latest attack on trees at Boonerah Point on Lake Illawarra has prompted Shellharbour City Council officers to intensify investigations into the ongoing problem.
Several trees were cut down this week at a site near where 15 trees were poisoned in July.
The council's city development group manager, Grant Meredith, said the council was taking the matter very seriously and would be using whatever means possible to identify the culprits.
During the past three years, hundreds of trees have been poisoned or removed along the lake at Mt Warrigal.
Last month, council staff also identified several mangroves that had been poisoned on the mudflats near the point.
The council wants anyone with information to contact them.
The offence attracts a minimum fine of $1500 per tree, and up to $1.1 million if it is taken to court.