Story highlights The Trump administration will admit refugees from high-risk countries after taking additional screening measures.

Officials will also review the list of countries considered high risk every six months.

The move follows a 90-day review of security vetting procedures.

(CNN) The Trump administration announced new security screening measures on Monday meant to further vet refugees applying to enter the United States from certain high-risk countries.

The announcement follows a 90-day review period initiated as a follow-up to the administration's earlier travel ban.

"It's critically important that we know who is entering the United States," Secretary of Homeland Security Kirstjen Nielsen said in a statement. "These additional security measures will make it harder for bad actors to exploit our refugee program, and they will ensure we take a more risk-based approach to protecting the homeland."

The new, so-called "enhanced vetting measures" will affect refugees from the 11 countries deemed to warrant higher levels of scrutiny. The administration is not publicly identifying those countries, but according to the group Refugee Council USA, which represents refugee resettlement agencies and other non-governmental organizations, the list currently includes Egypt, Iran, Iraq, Libya, Mali, North Korea, Somalia, South Sudan, Sudan, Syria and Yemen.

A senior administration official who briefed reporters Monday said the move would "improve our ability to detect terrorists, criminals, and other nefarious actors."

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