Nationwide Starbucks Closings Leave Customers' Cups Dry

May 24, 2012— -- Thousands of Starbucks customers left with empty mugs Wednesday as mysterious store closures beset caffeine-needy commuters nationwide.

At one Ohio Starbucks, caffeine-deprived customers were greeted with an empty parking lot and a magic-markered "closed for maintenance repairs" sign.

WCPO, ABC's affiliate in Ohio, asked disappointed customer Katie Shaw if she would survive without her regular drink.

"I think I might, but I don't know," she joked. "I'm pretty crushed right now."

"Less than 500" locations opened late because overnight maintenance took longer than usual because of "water pressure issues," Starbucks spokesman Jim Olson told ABC News. The maintenance involved in-store water filtration systems.

Twitter and other media reports indicate that stores were closed on the East Coast in Florida, New Jersey and New York as well as Indiana, Kentucky, Ohio, Pennsylvania, and South Dakota.

The problem could have led to equipment failure, and Starbucks wanted to ensure employee safety.

"Obviously when you have water pressure issues… you want be as cautious as possible," Olsen said.

Most locations were closed from about 7 a.m. until noon before reopening. Some stores opened, but didn't serve all types of beverages until later in the day.