WALLINGFORD, CT — Two "underperforming" Smashburger locations in Milford and Wallingford closed abruptly this week, a spokesperson for the national hamburger chain confirmed Wednesday.

"We constantly review our restaurant portfolio and make strategic decisions to better our position for the future," Katy Michael of Smashburger said in an email to Patch. "Unfortunately, from time to time, we must close underperforming stores that don't meet our performance standards. Regretfully, Smashburger closed the Milford and Wallingford locations. We are very grateful to our valued associates and everyone who has supported us in the local community over the years." Employees of the Smashburger in Wallingford received phone calls on Sunday night informing them of the closure, according to the New Haven Register. The restaurant was closed on Monday.

A sign posted on the door at the Wallingford location, 1094 North Colony Road, read "Thank you for your business over the last three years. We have closed for business." The Wallingford Smashburger was housed in the same building as Chipotle in the Lowe's Plaza. Chick-fil-A and Panera Bread are also in the same plaza.

Several customers and former employees began reporting on social media earlier this week that the Milford Smashburger location, 1590 Post Road, was also closed. A call to the restaurant's phone number went to voicemail. The four other Smashburger locations in Connecticut — including Enfield, Manchester, Southington and Waterford — remain open.