Police are investigating a malicious oil spillage which forced a major road racing event to be abandoned.
The Mid-Antrim 150 was cancelled on Saturday after organisers discovered much of the course at Clough had been sabotaged.
A mixture of oil and diesel was found at various points on the circuit.
Although a major clean-up operation got underway, the event - the penultimate round of the 2011 Irish Road Racing Championship - was called off around 12.30pm.
The PSNI was informed and a spokesman confirmed yesterday that an investigation into the incident was ongoing.
He said a deliberate spillage was one line of inquiry being pursued.
Clerk of the Course Jack Agnew said it would have been wrong to risk riders' safety by proceeding with the event.
"We did our best to run the event but I wasn't prepared to risk the safety of riders," he said.
"We are determined that the race will run again in 2012."
Dungannon rider Ryan Farquhar had inspected the circuit before the races were called off, and said it was hugely disappointing that the event had to be abandoned.
"The club had done a good job cleaning up the oil, but when rain hit the circuit some riders were not sure as to race or not and some were against it," he said.
"Accidents and weather can disrupt things and we accept that, but this was something totally different and it's not fair to all those people - riders, organisers, fans - who make the meeting happen."
Saturday's cancellation is the latest blow to hit road racing, with the sport struggling to survive financially in the depressed economic climate.
Ulster Unionist MLA Robin Swann said the cancellation was a huge blow to the road racing fraternity in North Antrim.
"It looks like this was a deliberate and frankly disgraceful move to stop the event from going ahead," he said. "The Mid-Antrim 150 is a highlight on the road racing calender and those selfish individuals who caused the oil slick have ruined the hard work put in by the event organisers."
Mr Swann said the decision to cancel the races had been the right one.
The Mid-Antrim 150 road races were first run in 1946 and are the second last event of the road-racing season.
Among those who were due to race on Saturday were Ryan Farquhar and Adrian Archibald, two of the sport's biggest names.