At least 40 people in seven states have died amid the severe weather outbreak, officials said Sunday.

At least 12 deaths were reported in Missouri, the most of any state, officials said.

On Sunday morning, Alabama Gov. Kay Ivey said at least three people were killed in her state on Saturday.

"Yesterday's severe weather impacted most of Alabama," Ivey said in a statement. "Unfortunately, we have learned of the loss of at least two of our fellow Alabamians -- one life in Plantersville and one in Winterboro."

Ivey said 52 of Alabama's 67 counties reported damage from the severe weather outbreak and that a damage assessment was continuing.

"The sun has risen in Alabama, though," Ivey said. "We pray for those lives we lost, as well as those who were injured. And we pray for our first responders, emergency management officials, and linemen who are doing incredible work on the ground right now."

At least eight deaths were reported in Kansas; six people in Mississippi were killed; four people perished in Texas; three people died in Arkansas; and four people were killed in Oklahoma, officials said.

ABC News' Victoria Arancio

As the cross-country storm continues to spread across the United States, cities north of Tampa, Florida, are now under tornado warnings.

Zephyrhills, Pasadena Hills and Crystal Springs are under alert until 7:30 p.m. ET, according to the National Weather Service.

Mississippi Governor Tate Reeves shared a storm update Sunday afternoon after signing a state of emergency declaration Saturday night.

The governor said preliminary information shows as many as 12 tornadoes could have ripped through the state in the cross-country storm.

The storm left six dead and 27 injured in Mississippi, but the three people reported missing were found alive, Reeves said.

Twenty-three counties in the state are reporting damage and 12 filed emergency requests, the governor said.

-ABC News' Darren Reynolds

President Donald Trump took to his social media platform on Sunday to say that the White House is monitoring the spate of tornadoes and storms impacting the Midwest and South.

Thirty-seven people have been killed in the cross-country storm system, according to officials.

Trump said the National Guard has been deployed to Arkansas.

"My Administration is ready to assist State and Local Officials, as they help their communities to try and recover from the damage," Trump wrote.

"Please join Melania and me in praying for everyone impacted by these terrible storms!" the president added.

-ABC News' Hannah Demissie

At least six people have died in Mississippi in the outbreak of tornadoes Saturday, the governor said.

Another three people are missing and 29 people are injured, Gov. Tate Reeves said in a social media post Saturday night.

"Please pray for those who lost their life, those who are missing and those leading the search efforts, those who are healing, and their families," Reeves said in the post.

Three of the deaths -- including of a juvenile -- were in Tylertown, not far from the Louisiana state line, according to Tylertown Police Chief Jordan Hill.

The governor signed a state of emergency declaration that he said will allow the state to further mobilize state resources. Overall, 21 counties sustained storm damage and about 16,000 are without power, the governor said.

The deaths in Mississippi brings the total death toll from an outbreak of severe storms over the past day to 34 people as of Saturday evening.