South Korean authorities are investigating a man who served in the country’s army on charges of stealing a device used in military explosives to potentially carry out an Islamic State (ISIS/ISIL) terrorist attack, the defense ministry announced on Friday.

“The man is charged with stealing military equipment and violating the anti-terrorism act by allegedly attempting to join the Islamic State,” an unnamed South Korean defense ministry official said, according to the Korea Times. “The (ministry’s) Criminal Investigation Command referred the case to the prosecution on Monday.”

Local news outlets learned from defense ministry officials that the 23-year-old man, identified only by his surname Park, is accused of stealing one spark plug for explosives in October 2017 while he was training at an Army engineering unit as an explosive specialist.

As of Tuesday, the army had relieved Park of his enlistment.

The Yonhap News Agency adds:

Investigators also found a video clip on his cellphone on how to make homemade ammunition as well as a mobile app used by IS [Islamic State] members and supporters. Also found at his home was a machete that looks similar to broad blade knives that have been used by terrorists, officials said.

The suspect had collected video clips and other materials related to IS and posted them online since 2016, the officials said, adding that he is suspected of exchanging emails with suspected members of the militant group.

FBI officials reportedly flagged the suspect in November 2017 for accessing an ISIS-linked website using an IP address from South Korea, prompting local authorities to start investigating him.

Park claims “curiosity” drove his alleged acts, denying any criminal intentions, Yonhap learned from an investigator.

“[The suspect has said that] he downloaded the IS-related app out of curiosity, and he posted the group-related video clips only on [South Korea’s right-wing website] Ilbe several times,” the unnamed investigator declared.

In June 2016, South Korea’s primary spy agency warned that ISIS was seeking to instigate terrorist attacks against two military facilities manned by the U.S. troops and civilians in the country.

At the time, the Hankyoreh daily reported:

The threat of terrorism against a South Korean national by ISIL is not the first. In February [2016], the group used YouTube to share personal information for civilians from several countries, including 20 South Koreans. At the time, no clear reason was identified for why they would be targeted.

“ISIL is broadening the range of its terrorism from Europe into Asia and encouraging terrorism by emerging sympathizers,” South Korea’s National Intelligence Service (NIS) declared in June 2016.

“We are closely monitoring the activities of international terror groups,” it added.

In December 2018, a South Korean court sentenced a Syrian man to three years in prison for promoting ISIS-linked terrorism in the Asian country.

“The defendant continuously promoted activities and ideas related to Islamic State on his Facebook,” the court proclaimed, according to United Press International (UPI). “He had a [encrypted messaging app] Telegram link to a secret chatting room with IS members,” it added.

In recent years, South Korean authorities have expressed concerns about impressionable local teens joining ISIS.