McALLEN, Texas - A Mexico City toddler who became the first swine-flu death on U.S. soil spent a day with his family shopping at a huge Houston indoor mall the day before he began to show symptoms.

Cameron County Judge Carlos Cascos, who spoke with the boy's aunt, said the family spent three nights in Houston just before he fell ill. After spending time in Houston, including at The Galleria mall, they drove the 350 miles back to Brownsville, where he was hospitalized on April 8.

When the hospital there could no longer care for the 23-month-old boy, he was medically transported to Texas Children's Hospital in Houston on April 14. The boy, who had underlying health problems, died Monday.

Health officials earlier insisted the boy posed no contagion threat to Houston because he had no outside contact there and was kept away from other patients in the hospital. His family has shown no symptoms.

"It's important because we don't know where he contracted it," Cascos said. "It could've been in Houston or somewhere on the way."

Houston officials did not know of the boy's earlier visit to the city, a spokesman for the mayor said Thursday.

"We have asked (the epidemiologist studying the case) to go back and double check," Frank Michel, a spokesman for Houston Mayor Bill White.

Cascos declined to identify the family, citing privacy.