Communities across the eastern United States were clearing away downed trees and power lines Tuesday after severe storms killed at least two people, damaged homes, cut electricity to more than 1.1 million homes and businesses, and canceled or delayed thousands of flights.

Forecasters received more than 900 reports of wind damage from Monday’s storms. Nearly 300 of those reports of building damage or downed powerlines and trees came from North Carolina and South Carolina, according to the Storm Prediction Center.

A spokesperson for Baltimore Gas and Electric, Maryland’s largest power utility, called the destruction “catastrophic.”

“This is damage that if you worked in electric distribution at BGE for your entire career, you may see it once,” Nick Alexopulos said at a news conference Monday night.

The storms spawned tornado watches and warnings in 10 states from Tennessee to New York with more than 29.5 million people under a tornado watch Monday afternoon.

A preliminary assessment of damage in Knoxville, Tennessee, found that an EF-2 tornado touched down there with winds up to 130 mph (209 kph) and a path as wide as 200 yards (meters), the National Weather Service office in Morristown, Tennessee, announced Tuesday. The office said it will continue to assess the damage across the area.

Damage was extensive across the Knoxville Utilities Board’s service area, and while power was restored to many customers, thousands were still without on Tuesday morning, board spokesperson Gerald Witt said.

“We’ve made substantial progress,” Witt said. “But there’s still widespread and severe damage that remains and work is expected to take multiple days.”

More than 1.1 million customers were without power Monday evening across Alabama, Georgia, South Carolina, North Carolina, Maryland, Delaware, New Jersey, Pennsylvania, Tennessee, West Virginia and Virginia, according to poweroutage.us.

By noon Tuesday, the number of customers without power had dropped to about 240,000 in Pennsylvania, North Carolina, Maryland, Georgia and Tennessee.

In Westminster, Maryland, dozens of vehicles were trapped amid a string of power lines that fell like dominoes onto a highway. No injuries were reported. Utility crews turned off the electricity to the power lines, and the 33 adults and 14 children in the vehicles were able to get out safety, Maryland State Police Superintendent Col. Roland Butler said at a news conference Tuesday.

First responders and others worked as a team and saved lives Monday night, Gov. Wes Moore said.

“There were people who were stuck and stranded in cars who were able to sleep in their own beds last night,” he said. “And that’s because of the work of everybody who moved and our first responders who made it so.”

By Monday night, more than 2,600 U.S. flights had been canceled and nearly 7,900 delayed, according to flight tracking service FlightAware. The trouble continued Tuesday with hundreds of delays and dozens of cancelations. The Federal Aviation Administration, which rerouted planes around storms on Monday, warned Tuesday that low clouds and winds could impact airports in New York, Philadelphia, Washington, D.C., Las Vegas and San Francisco and thunderstorms could mean delays in Boston, Atlanta, Florida and Chicago.

In Anderson, South Carolina, a large tree was uprooted and fell on a 15-year-old boy who arrived at his grandparent’s house during the storm Monday, according to the Anderson County Office of the Coroner. The high school sophomore’s death was ruled accidental and classified as a death resulting from a severe weather event, officials said.

In Florence, Alabama, a 28-year-old worker in the parking lot of an industrial park was struck by lightning and died from his injuries received during the storm Monday, police said in a social media post.