Deputies were dispatched to the single-vehicle crash at about 1:45 p.m. on US-90.
Authorities said the driver lost control and the vehicle rolled over several times, leaving a long trail of debris and personal items.
"It appears that there were some new clothes that they were, perhaps, going to be wearing later today, and even some eggs, you know, like they were going to be enjoying the day," Sheriff Ed Gonzalez said.
Gonzalez said the major crash involved a family of five: 25-year-old mother Tiffany Rodríguez, a 26-year-old father, a 5-year-old daughter named Ariella, a 2-year-old boy, and a 2-month-old baby girl.
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Officials say that neither of the parents were wearing seatbelts, and all three kids were in car seats. Gonzalez said it is unclear if the children were properly secured in their car seats.
Tiffany and Ariella were pronounced dead at the hospital. The father and his other two kids were taken to the hospital for their injuries, but they are expected to survive.
"Just this weekend, we have seen a number of people die on our roadways for different factors, but just another tragic scene, and again, on Easter Day," Gonzalez said.
Deputies believe that speed was a contributing factor to the major crash. They are still investigating whether drugs or alcohol played a role.
Gonzalez said this crash makes 45 people total who've died in crashes in Harris County since the start of the year.
"It is really astonishing, and as much as we try to educate our community, we continue to see the same things," Gonzalez said. "I want to be very clear that these crashes are all preventable."