HOUSTON (AP) — Fast-moving thunderstorms pummeled southeastern Texas for the second time this month, killing at least four people, blowing out windows in high-rise buildings, downing trees and knocking out power to more than 900,000 homes and businesses in the Houston area.

Officials urged residents to keep off roads following Thursday’s storms, as many were impassable and traffic lights were out. The storm system moved through swiftly, but flood watches and warnings remained Friday for Houston and areas to the east.

Houston Mayor John Whitmire said four people died during the severe weather. At least two of the deaths were caused by falling trees and another happened when a crane blew over in strong winds, officials said.

Houston’s streets were flooded and trees and power lines were down across the region. Whitmire said wind speeds reached 100 mph (160 kph) “with some twisters.” Whitmire said the powerful gusts were reminiscent of 2008’s Hurricane Ike, which pounded the city.

“Stay at home tonight. Do not go to work tomorrow, unless you’re an essential worker. Stay home, take care of your children,” Whitmire said in a Thursday evening briefing. “Our first responders will be working around the clock.”

Gulf Coast states could experience scattered, severe thunderstorms with tornadoes, large hail and damaging winds. Heavy to excessive rainfall is possible for eastern Louisiana into central Alabama on Friday, the National Weather Service said.

In Houston, hundreds of windows were shattered at downtown hotels and office buildings, with glass littering the streets below, and the state was sending Department of Public Safety officers to secure the area.

“Downtown is a mess,” Whitmire said, adding that there was a backlog of 911 calls first responders were working through.

The ferocious storms also moved into neighboring Louisiana and left more than 215,000 customers without power. More than 100,000 Entergy Louisiana customers in the New Orleans area lost power, NOLA.com reported.

The weather service forecast office for New Orleans and Baton Rouge issued a flash flood warning through Saturday.

At Minute Maid Park, home of the Houston Astros, the retractable roof was closed due to the storm. But the wind was so powerful it still blew rain into the stadium. Puddles formed on the outfield warning track, but the game against the Oakland Athletics still was played.

The Houston Independent School District canceled classes Friday for some 400,000 students at all its 274 campuses.

Flights were briefly grounded at Houston’s two major airports. Sustained winds topping 60 mph (96 kph) were recorded at Bush Intercontinental Airport.

About 900,000 customers were without electricity in and around Harris County, which contains Houston, according to poweroutage.us. The county is home to more than 4.7 million people.

The problems extended to the city’s suburbs, with emergency officials in neighboring Montgomery County describing the damage to transmission lines as “catastrophic” and warning that power could be impacted for several days.

Heavy storms slammed the Houston area during the first week of May, leading to numerous high-water rescues, including some from the rooftops of flooded homes.

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Baumann reported from Bellingham, Washington, and Weber from Los Angeles.