Jimmy John's announced Wednesday that customers' credit card data may have been stolen from hundreds of its stores, including 18 Michigan locations, between June and September. About 216 stores were affected nationally by the breach, but it's unclear how many customers were actually impacted. None of the chain's stores in West Michigan were affected by the breach.

The sandwich chain said it learned of the possible security breach on July 30th. 

The company said the security breach has been contained, and that the cards affected by the breach appear to be those that were swiped at the stores and not those that were entered manually or online.

Customers' card numbers, the cardholder's name, verification code and the card's expiration date may have been compromised.

Here are the affected restaurants in Michigan:

1535 E. 12 Mile Rd., Madison Heights --- 6/16/2014 - 8/7/2014

40846 Van Dyke, Sterling Heights --- 6/16/2014 - 8/7/2014

4790 S. Hagadorn Rd., East Lansing --- 6/16/2014 - 8/2/2014

143 N. Harrison Ste. 100, East Lansing --- 6/16/2014 - 7/30/2014

537 W Cross Street,Ypsilanti --- 6/16/2014 - 7/30/2014

7568 E. 9 Mile Rd., Warren --- 6/16/2014 - 8/13/2014

31204 Beck Rd., Novi --- 6/26/2014 - 8/1/2014

6535 N. Canton Center Rd., Canton --- 6/27/2014 - 8/13/2014

1260 S. 11th St., Niles --- 7/1/2014 - 8/2/2014

33177 W. 8 Mile Rd., Livonia --- 7/1/2014 - 7/30/2014

36324 Van Dyke, Sterling Heights --- 7/1/2014 - 8/1/2014

4087 W. Maple Rd., Bloomfield Hills --- 7/1/2014 - 8/3/2014

3220 U.S. Hwy 41 W, Marquette --- 7/1/2014 - 8/8/2014

39755 Grand River Ave., Novi --- 7/23/2014 - 8/1/2014

413 S. Main St., Royal Oak --- 7/23/2014 - 8/1/2014

37671 Six Mile Rd. B218, Livonia --- 7/23/2014 - 8/2/2014

719 Washington Ave., Bay City --- 7/23/2014 - 8/1/2014

5601 Sashabaw Rd., Clarkston --- 7/23/2014 - 8/1/2014

Jimmy John's posted a complete list of stores impacted on its website.