A staff manual said pasting text into tools such as Google Translate and Bing was "the most efficient approach".

News site ProPublica said online tools often mistranslated sentences and misinterpreted nuance and slang.

But the USCIS told the news site that checking social media posts was a "common-sense measure".

The agency said "information collected from social media, by itself, will not be a basis to deny refugee resettlement".

The United States now requires nearly all applicants for US visas to submit details of their social media accounts.

The staff manual explains procedures to be used when vetting people whose spouse or parents have already been granted refugee status in the US.

It was obtained by the International Refugee Assistance Project and shared with ProPublica.

It acknowledges that "occasionally" the online translation services may not fully understand "dialect" or colloquial language.

It says individual officers can decide whether to request expert translation services.