Minnesota's Department of Natural Resources has warned anyone who paid for purchases at Tettegouche State Park between Aug. 22-25 to look for suspicious activity on their credit card accounts after malware was discovered on the park's computers. 

The malware was found after a noticeable uptick in unusual activity, according to a report by the Associated Press. 

Around 400 credit card transactions occurred during that time period, but authorities from the Natural Resources department are unsure whether attackers were able to access credit card numbers. No other systems within the state or department networks were infected, according to the AP report.