SAN FRANCISCO — An American citizen who’d been working as a school teacher in Thailand was arrested at the San Francisco International Airport and later charged with having child sexual abuse material on his phone, court records show.

Zachary Snoderly, 36, is in federal custody facing charges of possessing child pornography. Federal authorities allege that Snoderly’s electronic devices were found to contain more than 100 gigabytes of child pornography, including what “appeared to be snapshots of children in public places and what appeared to be minor children in a classroom setting,” according to the criminal complaint.

Snoderly booked a June flight to the United States, hoping to visit his father in Idaho. But he never got past the San Francisco airport. Prosecutors say that Customs and Border Protection agents had been notified to place Snoderly on “lookout for secondary inspection and questioning related to possession of child pornography.”

The criminal complaint doesn’t say how Snoderly became a suspect, but alleges that once agents asked if he had “digital contraband,” he replied, “probably.”

“When CBP asked Snoderly to clarify which type of contraband, Snoderly stated ‘child pornography.’ He told CBP that he used Telegram to download child pornography,” the criminal complaint says. This led to a search of his phone, laptop computer and hard drives.

During his interview, Snoderly said he has been living in Thailand for 11 years and works as a second grade teacher there, the complaint says.

Snoderly was arrested on June 20 but later released, pending a full review of his electronic devices. On Aug. 21, though, agents learned that Snoderly had obtained a new passport — the one he was arrested with had been seized by investigators — and booked a return trip to Thailand on Aug. 24. Agents arrested Snoderly before he could board the flight and he was charged the following day, court records show.

Snoderly appeared in court last week, where a judge ordered him to remain in federal custody. He is next due in court on Sept. 11, records show.