(Reuters) - Doughnut chain Krispy Kreme said on Wednesday that unauthorized activity on a portion of its information technology systems has disrupted certain operations, including online ordering in the United States.

Shares of the company were down about 2% in premarket trading.

After being notified of the incident on Nov. 29, the company has initiated an investigation and is working with external cybersecurity experts to mitigate the impact, it said in a regulatory filing.

Krispy Kreme said the expected costs related to the incident, including the loss of revenue from digital sales, are "reasonably likely to have a material impact" on its results of operations.

The company's shops globally are open and consumers are able to place in-person orders, it said.