CHICAGO (CBS) — Computers at Starbucks in Chicago, and apparently across the country, crashed on Tuesday morning, leaving customers unable to order their morning lattes.

Computers were down at two locations in the Loop, according to witnesses. Workers there were giving away free regular coffee as compensation.

As people learned of the free coffee offer, lines began to form outside downtown stores. According to witness accounts, the systems started to come back online in the Loop around mid-morning.

At a location underneath Daley Plaza, near the Washington Street Blue Line, workers were giving away food as well and customers cleared out the shelves.

It was not immediately clear what caused the malfunction or how many stores were affected.

On Twitter, people across the country were reporting similar issues.

Gotta hand it to @Starbucks Their computers are down nationwide and they are giving out free iced and hot coffee. #TakeCareOfYourCustomers — Mike Parise (@mikemj23) May 16, 2017

Starbucks computers are down. If this is a cyber attack, this means war! — Ryan Stubenrauch (@Rstubenrauch) May 16, 2017

According to Starbucks, they were working overnight to install a technology update in U.S. and Canada, saying, “A limited number of stores are offline because of a glitch, so cash only.”

Starbucks said they are working to have the computers back up as soon as possible.