The project was underway “without environmental authorization” on the Paris Saint-Germain and Brazil national team player’s luxury property in Mangaratiba, some 130 kilometers (80 miles) from Rio de Janeiro, the mayor’s office said in a statement.
They also discovered unauthorized excavation and movement of earth, stones and rocks, as well as the use of beach sand without a permit.
“The next step will be to make an assessment of the irregularities found and issue a fine which, according to estimates and in view of the environmental damage caused, will not be less than five million reais (about $1 million),” the mayor’s office said.
Neymar’s representatives in Brazil have not responded to AFP’s request for comment.
The footballer’s father, Neymar da Silva Santos, was on site during the inspection and can be heard arguing with officials in a video published by authorities and carried by local media.
Neymar bought the property in 2016. According to local media, it sits on 10,000 square meters (2.5 acres) of land and includes a helipad, spa and gym.
The 31-year-old striker is currently recovering from an operation on his right ankle, which he underwent in Doha, Qatar, in March.
He has not played since February, and doubts have arisen as to whether he will remain at PSG.