Perth County OPP are investigating after a break-in at a St. Marys-area mink farm that saw 6,800 animals freed from their cages, the second release in as many months.

The incident - on a farm on the west side of Road 125 just north of St. Marys - is believed to have happened between 11 p.m. Tuesday and 1 a.m. Wednesday.

Police say someone cut wide openings in the perimeter fence in several locations, then entered four sheds and released thousands of mink from their cages before fleeing.

Employees have reportedly returned many of the mink to their cages, but some remain missing.

Another commercial mink farm - on Perth Line 9 east of St. Marys - was the target of similar mischief at the end of May.

In that case, 1,600 mink were released, and the incident prompted the Canada Mink Breeders Association to offer a $75,000 reward for information leading to a conviction in the case.

While no suspects have been identified, some in the industry believe animal welfare activists may be involved.

However, an estimated 130 mink died in the days following the release, some due to being hit by vehicles or exposure to the cold and others who were too young to be without their mothers.

Anyone who may have seen suspicious activity in the area is asked to contact OPP at 1-888-310-1122 or Crime Stoppers at 1-800-222-TIPS.

With files from CTV Kitchener