The Trump administration on Friday expanded its immigration visa ban  to include six new countries.

The countries are Nigeria, Eritrea, Tanzania, Sudan, Kyrgyzstan and Myanmar with exceptions for immigrants who have helped the US.

The latest addition comes three years after President Donald Trump signed the first travel ban.

Officials of the Department of Homeland Security and the State Department said Nigeria was added to the list because of an “elevated risk and threat environment in the country,”

All six countries have substantial Muslim populations. The total number of countries now on the restricted travel list stands at 13.

The new restrictions only include categories of immigration visa applicants. All immigrants from Myanmar, Eritrea, Kyrgyzstan and Nigeria will be banned from the United States. However, only green card lotteries will be restricted from Sudan and Tanzania.

The restrictions apply to immigrant visas, but not students, other temporary visitors or refugee processing.

The proclamation signed by President Donald Trump on Friday is expected to take effect on February 22.