Saturday's Mid Antrim 150 race day has been cancelled after oil, glass and nails were deposited on sections of the circuit overnight.
The PSNI said the items had been "deliberately" spilled on the Drumagrove Road, Cloughwater Road and Dunbought Road parts of the course.
The organising committee posted a brief statement on Saturday morning to confirm the event had been cancelled.
Read more: Mid-Antrim 150 road races to go-ahead as planned this weekend
It read: "Sadly due to circumstances beyond our control race day of Mid Antrim 150 road race is cancelled."
The PSNI said they received a report "in the early hours of Saturday morning" and "efforts are ongoing to clean the roads".
They police statement added: "Police in Ballymena received a report in the early hours of Saturday 10th September that glass, nails and oil had been deliberately spilled on Drumagrove Road, Cloughwater Road and Dunbought Road.
"Efforts are ongoing to clean these roads."
Organisers had come in for some criticism after proceeding with the event following the death of Queen Elizabeth II on Thursday.
On Friday morning the Mid-Antrim committee said: "After considerable talks with all the appropriate authorities The Mid Antrim 150 road race will be going ahead. This a decision that has not been taken lightly.
"We will be paying tribute to the late Queen Elizabeth II throughout the weekend. We hope that everyone can respect our decision."
Practice took place on Friday, as the event returned for the first time since 2016.
This is the second time the Mid-Antrim 150 has been cancelled because of oil and other substances being deposited on the track. A similar incident happened back in 2011.
The police have appealed for anyone with information to contact them.
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