BIRMINGHAM, Ala. (AP) — With lowered flags and somber ceremonies, Alabama will pause Tuesday to mark the 10th anniversary of a horrific tornado outbreak that killed more than 250 people statewide, caused billions in damage and reshaped entire communities.

Gov. Kay Ivey issued an order for flags statewide to be lowered to half-staff and proclaimed a “Day of Remembrance” for a “horrible event that has impacted the state of Alabama forever.”

In Tuscaloosa, where dozens were killed and entire neighborhoods were demolished, three new memorial plaques will be dedicated during ceremonies to honor victims and recall the horrors of April 27, 2011. The University of Alabama will toll its 25-bell carillon, Denny Chimes, 53 times to honor each of the people who died in the city.

Tornadoes plowed across the Eastern U.S. over four days, killing more than 320 people in six states and causing an estimated $12 billion in damage. Thousands were injured in hardest-hit Alabama, and thousands of homes, businesses, churches and other structures were destroyed. Cleanup costs exceeded $100 million in Tuscaloosa alone.

To help document the outbreak, the National Weather Service created an extensive online archive with details about the more than 60 twisters that hit Alabama.

In tiny Hackleburg, which still lacks sufficient housing and retail businesses because an EF-5 twister wiped out most of the town businesses and many homes, killing 18 people, residents will gather on a road in an intersection in the afternoon to form a human cross, said Mayor Darryl Colburn.

“I hope everyone can make it out and take a moment to remember the friends and family members we lost that tragic day, but also recognize the hope, strength and resilient attitude we’ve shown as a Town and Community to continue to come back stronger,” Colburn said in a message on social media.

In the small town of Phil Campbell, where 27 were killed in the same tornado, the high school band planned an evening concert that will conclude with a special piece written to commemorate the anniversary. A community group in the tight-know Shoal Creek Valley, where a dozen were killed, sold commemorative T-shirts with the words: “Strength is what we gain from the trials we survive.”

In northeast Alabama’s DeKalb County, where nearly three dozen people died, a community service was held Saturday in Rainsville to remember the outbreak.