That has triggered concerns for parents of students studying or planning to study in the US. South Korean students are the third-largest among international students in the US, behind those from India and China.

The US administration ordered its missions abroad to stop scheduling new appointments for student and exchange visitor visa applicants as the state department prepared to expand social media vetting of foreign students, according to an internal cable seen by Reuters on Tuesday.

The Trump administration has sought to ramp up deportations and revoke student visas as part of wide-ranging efforts to meet its hardline immigration agenda.

“My clients, parents are calling me constantly today to figure out what is going on,” said Park Hyuntae, head of Worldnet US Overseas Edu Center, an agency in Seoul that assists South Korean students.

“Those who already scheduled those interviews and will apply for interviews both are worried, nervous, but cancellations of existing interviews haven’t happened yet as far as I know,” he said.

Park said the visa interview pause could cause delays in starting the school year, and that he was advising clients to be cautious over what they post online.

“I am telling them, especially male students, do not post anything extreme or disgusting on social media, like pictures of grenades or weapons,” he said.

An email reviewed by Reuters from a liberal arts college told students overseas that scheduled visa interviews might be postponed and suggested they gave their “socials a little attention.”

Stiff competition to get into South Korea’s top universities has driven many students to study abroad, according to the US International Trade Administration.

One South Korean student who studies in the US said he had friends who were unable to schedule visa interviews, and that he was concerned about his own plans to try to work in the US after graduation.

“I think what is now the US is a lot different than the US in the past,” he said, asking not to be identified.