U.S. Rep. Maxine Waters, D-California, has cancelled a planned trip to Birmingham due to what she told CNN was a 'very serious death threat.' She was scheduled to speak Friday at an annual conference for black female politicians, local officials and community leaders.

Waters was supposed to address an audience of black women for the National Organization of Black Elected Legislative (NOBEL) Women's Annual Legislative Conference, which starts today and ends Sunday. But NOBEL President Karen Camper, a state representative from Tennessee, confirmed that Waters was no longer coming because of security reasons.

Waters said Thursday that she canceled events in Texas and Alabama after a "very serious death threat" made against her.

In a statement reported by CNN, the California Democrat said that after President Donald Trump took aim at her Monday on Twitter, "even more individuals are leaving threatening messages and sending hostile mail to my office."

"There was one very serious death threat made against me on Monday from an individual in Texas which is why my planned speaking engagements in Texas and Alabama were cancelled this weekend," Waters said in the statement.

A Waters spokeswoman did not immediately respond to a request for confirmation.

Waters has been rebuked by Republicans and Democrats after calling at a Los Angeles rally last weekend for demonstrators to harass Trump's Cabinet officials wherever they go amid an escalating debate over immigration policy.

Taking to Twitter, Trump fired back by calling Waters "an extraordinarily low IQ person" and warning her to "be careful what you wish for."

According to CNN, Waters said in the statement that Capitol Police are investigating several other threats in which people have vowed "to shoot, lynch, or cause me serious bodily harm."

"Maxine Waters' strength, determination and spirit always inspires us and will permeate throughout this conference," Camper said in a statement.

Waters' cancellation comes during a time when both Republican and Democratic lawmakers are criticizing remarks she made during an immigration rally telling citizens to publicly confront members of Trump's administration. Her statement was made in response to Trump's "zero tolerance" immigration policy, which led to the separation of children from families at the Mexico border.

"Let's make sure we show up wherever we have to show up," Waters said during the rally. "And if you see anybody from that cabinet in a restaurant, in a department store, at a gasoline station, you get out and you create a crowd. And you push back on them. And you tell them they're not welcome anymore, anywhere. We've got to get the children connected to their parents."

Multiple lawmakers, such as House Majority Kevin McCarthy, have asked Waters to apologize for her statements.

"We have to have civility," McCarthy told Fox News during an interview on Monday. "I can disagree with somebody philosophically, but to personally attack -- to remove somebody and not serve them? What's interesting to me, the people who claim tolerance seem to be the most intolerant in this process."

This story was updated at 2 p.m. to include a statement from Rep. Karen Camper and at 9:13 p.m. to include contributions from The Washington Post.