The unnamed physical education teacher at Singapore International School, 52, was arrested by U.S. police in 2013 for storing around 1,000 images depicting child porn on his personal computer, Mai Tan Linh, deputy director of the Da Nang Department of Education and Training, said Tuesday.

The culprit was released after police failed to collect any evidence indicating child abuse, Linh added.

"The teacher was listed as a suspect back then. But following an investigation, no violations were uncovered so no further legal proceedings were conducted," he said.

In 2017, the teacher was employed at Singapore International School in Da Nang’s Ngu Hanh Son District based on his qualifications.

"He has been teaching here ever since. When we recently uncovered the information about him, we got worried and actively terminated our contract with him," Linh commented.

In a letter to the school’s parents, it said the teacher in question had been fired starting March 8, a day after the school received a report from a parent who found out about the teacher's past activity through a U.S. newspaper.

The school said its hiring practice was conducted in a stringent manner, with prospective employees required to report their personal information and legal status.

The U.S. teacher reported he had no criminal record.

All foreign teachers must provide legal and criminal records verified by relevant entities, the school stressed.

The U.S. teacher holds a bachelor’s degree in education and a license to teach physical education. He also carries appropriate documents required for employment in Vietnam, including a legal and criminal record.

Vietnam does not have a public list of sex offenders. It's not clear if other schools in the city or elsewhere would be informed of his situation.