Portland police are pursuing leads and increasing patrols throughout the city in response to a string of commercial burglaries that appear to be similar but might not have been committed by the same person or people.

Lt. Robert Martin, spokesman for the Portland Police Department, identified on Monday the 12 businesses that have been targeted since the break-ins began on July 28 when someone broke into Eyes on Rosemont at 152 Middle St.

There was no sign of forced entry into the businesses in some cases, Martin said in a news conference, noting that some of the businesses may have left their doors unlocked.

During an overnight patrol Sunday into Monday morning, officers found two establishments where the premises had not been secured. Martin said one establishment’s door was unlocked while another business had an unsecured ground-level window.

Squeaky Clean Laundromat, 64 Washington Ave., and Others!, a coffee shop in Monument Square, were the latest businesses to have been burglarized, bringing the total number of break-ins to 12 over a period of three weeks.

There doesn’t seem to be any pattern to the commercial businesses that were burglarized. Based on the location and the products being sold, the burglaries seem to have been committed on a random basis. The businesses are located all over the city peninsula and range in use from an optometrist’s office, apparel designer and a shop specializing in juice smoothies to a hair salon, Thai restaurant and craft beer gastropub.

A surveillance video by Maine Juice Company at 129 Spring St. shows a male suspect using a pry bar to break in on Aug. 5. The man then poured liquid over the register before making off with about $600 in cash.

One of the co-owners of LB Kitchen on Congress Street told News Center Maine that someone broke into the breakfast and lunch restaurant and stole the cash register and safe. The burglar stole more than $700 in cash.

During the news conference at the Portland police station on Monday afternoon, Martin told reporters that investigators are treating the surge in burglaries as uncommon.

“We get these (burglary sprees) several times a year, a cluster of two or three,” Martin said. “But to have this many in such a short period of time is unusual for the city of Portland.”

No arrests have been made. Anyone who has information that could help Portland police solve these crimes is asked to call 207-874-8575.

Here is the complete list of commercial businesses that have burglarized, as provided by the Portland Police Department:

1) Eyes on Rosemont, 152 Middle St.

2) Maine Oyster Company, 38 Portland St.

3) Maine Juice Company, 129 Spring St.

4) Wallace James Clothing, 112 High St.

5) Boda, 671 Congress St.

6) Little Tap House, 106 High St.

7) Leavitt & Sons Deli, 200 Kennebec St.

8) Toni’s Touch, 26 Forest Ave.

9) LB Kitchen, 249 Congress St.

10) LIO Restaurant, 3 Spring St.

11) Squeaky Clean Laundromat, 64 Washington Ave.

12) Others!, 15 Monument Square.