Jon Leslie Lyons, an English teacher at Woodrow Wilson High School, was arrested Tuesday.
Lyons, 44, remained in custody Wednesday. A detention hearing was set for Friday afternoon, according to court documents.
Investigators said a Dallas Independent School District employee notified authorities last month that the district had discovered child pornography on a district-issued computer that was assigned to Lyons.
An investigator with US Customs and Immigration Enforcement said he met with the tipster, who was able to show him the photos of young girls in lewd poses.
When questioned, officials said Lyons admitted to having images of 13-year-old to 16-year-old nude teenagers on his home desktop computer and Apple iPhone.
He also said he had downloaded child pornography from the Internet to his phone as recently as the previous day, according to a news release from the U.S. Department of Justice.
"We are thankful that the Office of Homeland Security and U.S. Attorney's Office reacted so quickly after we provided them information in this case," DISD spokesman Jon Dahlander said in the news release. "If any parent or child has additional information that might be helpful to investigators, we ask that they contact the school or the proper authorities."
The school district is in the process of terminating Lyons’ employment, Dahlander said in a phone interview.
When asked if any DISD students were thought to be in any of the photos, Dahlander replied, “No, not that I know of.”
If convicted, Lyons faces five to 20 years in prison per photo and a $250,000 fine.