Sears Holdings, which wasn’t shy when it announced at the start of the year that it is closing 150 underperforming stores, has quietly added at least 30 more to the list.

Another 12 Sears stores and 18 Kmarts are among the locations that are closing, from Carson, Calif., to Hialeah, Fla., with most scheduled to shut their doors in July, based on calls to the stores, malls and confirmation in local media.

At the start of the year, the retailer pinpointed the 150 stores it said it would close. But it declined this week to provide a list of additional locations that are slated to shut since then, saying that it update store counts each quarter.

A spokesman for the troubled chain has made no secret of its plans to close additional stores.

“At the beginning of the year we said we would continue to strategically and aggressively evaluate our store space and productivity, and accelerate the closing of some unprofitable stores,’’ said Sears Holdings spokesman Howard Riefs in a statement. When the company reported quarterly results in March, it noted “that we will continue to accelerate our focus on our best stores, best categories and best members.’’

Sears, a retail stalwart, has been struggling alongside other traditional retailers like Macy’s and J.C. Penney who are trying to come up with a new formula to appeal to shoppers that increasingly bypass the mall to browse and buy online from Amazon and others.

One analyst says Sears’ store closings, along with those its rivals, will create an opportunity for other chains that might want to swoop in.

“Market share will be up for grabs. As Sears closes stores…there will be market share for department stores to take advantage of. However, we do note that Amazon is, of course, a worthy contender for capturing the majority of this share,” wrote Oliver Chen…