The department's Otago workplace services manager, Mark Murray, said while unusual statistically to have so many fatal accidents in one area at one time, it was coincidental.
Mr Murray said the message of workplace safety needed to be emphasised regularly.
Two of the three Waitaki fatalities involved all-terrain vehicles (ATVs) and the third a motorcycle.
Mr Murray said there were three areas of safety which needed to be addressed with vehicles: whether they were fit and proper for the purpose for which they were intended, were safety features working and were users trained for the terrain on which the vehicles would be used.
The first fatality occurred on a Georgetown dairy farm on October 6 when a 10-year-old boy riding a motorcycle collided with a four-wheel-drive vehicle.
On November 1, a farm worker, of African descent, died on a Ferry Rd dairy farm when an ATV she was riding rolled and landed on her. Last week, another dairy farm worker died when an ATV rolled.
Police say the worker, originally from India, was bringing cows to the milking shed on an Elephant Hill Rd property when the ATV went into a shallow drain area and rolled on top of him.
He died at the scene,The serious accident involved a tractor rolling on hill country at Tuapeka West, near Lawrence.
Mr Murray said there were generally more fatalities at this time of the year, but another factor was the influx of foreign workers on to farms who may not have experience in handling equipment.
That made a farm safety culture even more important.
Staff needed to be properly trained to mitigate the risks, he said..