McALLEN, Texas -- A Mexico City toddler who became the first swine-flu death on U.S. soil spent a day shopping at The Galleria in Houston one day before he began to show symptoms.

Cameron County Judge Carlos Cascos, who spoke with an aunt of the boy in Brownsville who made the Houston trip, said they spent three nights in Houston just before he fell ill and was hospitalized in Brownsville.

"We still believe, given the onset of symptoms and travel history, that the infection probably occurred in Mexico, and if he was infectious in Houston, it was for a very short time and represents very little risk," said Kathy Barton, with the Houston Health Department.

The hospital, city and health officials on Wednesday said the 23-month old boy had traveled from Mexico City to Brownsville, where he became sick. When the hospital in Brownsville, a city of 140,000, could no longer care for him, he was medically transported to Texas Children's Hospital. They said he had had no outside contact in Houston. The family has shown no symptoms.

Frank Michel, a spokesman for Houston Mayor Bill White, said Thursday the city knew of no earlier visit to Houston before the transport to the hospital.

"We have asked (the epidemiologist studying the case) to go back and double check," he said.

Calls seeking comment from Texas Children's Hospital were not immediately returned.

The earlier visit to Houston could be significant because those infected with the virus can be contagious one day before they show symptoms, according to the U.S. Centers for Disease Control. While the child may have had limited close contact with people outside his immediate family at The Galleria mall in Houston, the CDC says it is still not known how easiliy the virus spreads among people.

Cascos' timeline of the boy's visit, assembled after speaking with his aunt shows the boy was not only in Brownsville before he fell ill. Cascos declined to identify the family, citing privacy.

"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."

The boy's family flew from Mexico City into Matamoros, Mexico across the border from Brownsville on the evening of April 3. They spent that night and the night of April 4 at a Brownsville hotel. On Sunday April 5, the boy, three brothers, his mother and a cousin drove to Houston for a day of previously scheduled doctor's appointments for the mother and aunt. The boy, who officials said had several underlying health problems, did not see a doctor, Cascos said.

The day of doctor's visits on April 6 lasted from 9 a.m. to 5:30 p.m. Cascos was not sure what hospital the family visited that day.

The family spent April 7 shopping at the swanky Galleria mall in Houston. They spent three nights at another hotel near the mall, Cascos said.

Late April 7 or early April 8, the family began noticing some flu-like symptoms in the boy. They drove back to Brownsville April 8. By the time they returned, the boy had a fever and they took him to a family friend who was a doctor, Cascos said.

Within a day or two, the fever rose and they took him to another friend who was a doctor, where he was prescribed Tylenol, Cascos said. The fever continued to rise and April 13 they took him to Valley Baptist Medical Center in Brownsville.

By noon on April 14, the hospital said it could not give him the necessary care and recommended he be transferred. He was sent to Texas Children's Hospital in Houston. He died there April 27 and the CDC confirmed the boy had swine flu.

"Now this has a whole new dimension. Houston needs to look at their area, too, because that's where it probably occurred," Cascos said.

Statement From The Galleria

From: David Anderson, General Manager, Houston Galleria

"First and foremost, we want to extend our sympathies to the family of this little boy. We are so saddened by this tragedy and our thoughts and prayers are with them at this difficult time.

"It is important for us to announce that the Houston Department of Health and Human Services has closed their investigation into a link between the Houston Galleria and this occurrence.

"This is a community-wide health issue and we support the World Heath Organization and all other federal, state, and local health agencies, by encouraging everyone to be vigilant in combating the spread of this virus and following such recommended practices as washing your hands with soap and water frequently and thoroughly and covering your mouth and nose with disposable tissues when coughing or sneezing."