HOUSTON — A Mexico City toddler who traveled to Texas with family to visit relatives is the first confirmed death in the U.S. from swine flu.

The boy, who was nearly 2 years old, arrived in the border city of Brownsville with "underlying health issues" on April 4 and developed flu symptoms four days later, the Texas Department of State Health Services said. He was taken to a Brownsville hospital April 13 and transferred to the following day to a hospital in Houston, where he died Monday night.

The cause of death was pneumonia caused by the flu virus, Cameron County Judge Carlos Cascos said. Texas Children's Hospital, where the boy died, said in a statement he was suffering from "acute respiratory illness." The hospital planned a news conference later today.

Officials did not specify what underlying health issues the boy had before arriving in the U.S.

State health officials declined to identify the boy or his family, citing privacy concerns, medical confidentiality and "the absence of an obvious health threat from the boy to the public at large."

State health officials said the boy would not have been infectious when he flew from Mexico City to Matamoros, across the border from Brownsville. None of his close contacts have developed symptoms.

President Barack Obama said he wanted to extend his "thoughts and prayers" to the child's family.

Health officials in Brownsville are trying to trace his family's trip to find out how long they were in the area, who they visited and how many people were in the group, Cascos said.

The boy's family members "are healthy and well," Houston's health director, Dr. David Persse, said today at a news conference.

State health officials declined to identify the boy or his family, citing privacy concerns, medical confidentiality and "the absence of an obvious health threat from the boy to the public at large."

The Centers For Disease Control and Prevention confirmed the death earlier today.

Children, especially those younger than age 5, are particularly vulnerable to flu and its complications, and every year children die from seasonal flu.

According to the CDC, more than 20,000 children younger than age 5 are hospitalized every year because of seasonal flu. In the 2007-08 flu season, the CDC received reports that 86 children nationwide died from flu complications.

As of April 18, CDC had received reports of 55 seasonal flu-related deaths in children during the current seasonal flu season.

Swine flu is suspected of killing more than 150 people and sickening more than 2,400 in Mexico. U.S. health officials have confirmed 91 cases in 10 states.