Some residents in California, Oregon and Washington were woken up early Thursday morning when they received an earthquake alert test on a cell phone app early because of a time zone confusion, according to the United States Geological Survey.

The alerts were sent to users of the MyShake app, which sends a warning ahead of an earthquake.

A yearly alert test was scheduled to take place at 10:19 a.m. as part of The Great California ShakeOut, an earthquake drill, but some users received the alert test at 3:19 a.m.

“We acknowledge that no one wants to get a test message this early and we are working with our #ShakeAlert technical partner to determine what happened,” the USGS said on X/Twitter.

“There was likely a mixup between time zones set in the test alert system. Once @MyShakeApp makes a statement we will share the update. We appreciate your patience as we and our technical partners continue to learn and make improvements to the #ShakeAlert System,” another USGS post said.

The MyShake app was created by the UC Berkeley Seismology Lab, and uses information from the USGS to warn users so that they can take cover or slow vehicles or machinery down ahead of an earthquake.

On Wednesday, Californians received a real alert that signaled an earthquake about 40 miles from Sacramento.

The alert was sent through the MyShake app, as well as to cell phones that do not have it installed, through the use of Wireless Emergency Alerts that were developed to warn residents around the country of major emergencies.