Portland police are looking for clues after a vandalism spree left many coffee drinkers without their morning cup of joe.

Police said someone tried to shutdown some of the most popular Starbucks locations in Portland Friday morning by jamming the locks with glue or metal shavings.

Nearly a dozen locations in northwest Portland and the Pearl District had to open late. Some of the stores posted signs that said, “Sorry, we are closed due to vandalism.”

All stores were open and operational by 7 a.m.

No one has claimed responsibility for the vandalism. In the past, Starbucks in Portland have been targets of those opposed to the company’s growth.

Anyone with information is urged to contact Portland police.

Several Portland Starbucks Vandalized