SILVER BAY, Minn. — Authorities say malware has been found on computers at popular Tettegouche State Park on the North Shore of Lake Superior.

Computer security specialists found the malicious software on Aug. 25 after noticing a spike in unusual activity. So the Department of Natural Resources is advising anyone who charged purchases at the park from Aug. 22-25 to review their credit card accounts for suspicious activity and report any concerns to their card companies.

The DNR says about 400 credit card transactions took place at the park near Silver Bay during that period, though it has no evidence that credit card numbers were accessed.

DNR says the virus was isolated to computers at the park. No other DNR or state-owned systems were affected, including the state park reservation system and DNR website.