Washington (AFP) - President Donald Trump said Monday that the US would have to be careful about allowing Bahamian survivors of Hurricane Dorian into the country, warning there could be "very bad people" among them.

The previous day, several hundred storm survivors were prevented from boarding a ferry from the Bahamas to Florida because they lacked US visas -- an incident that a top American immigration official said was a mistake.

Speaking to reporters outside the White House, the president -- who has made strict immigration regulations a pillar of his presidency -- said that "everyone needs totally proper documentation."

"The Bahamas has some tremendous problems with people going to the Bahamas that weren't supposed to be there," Trump said.

"I don't want to allow people that weren't supposed to be in the Bahamas to come into the United States, including some very bad people and some very bad gang members and some very, very bad drug dealers."

Since he took office in 2016, Trump has made multiple efforts to stem the inflow of migrants, mainly from Central America.

When announcing his candidacy in June 2015, Trump made derogatory statements about immigrants from Mexico similar to what he said about Dorian survivors, warning they were bringing "drugs" and "crime," and were "rapists."

Mark Morgan, the acting commissioner of US Customs and Border Protection, said the ferry incident was a mistake and the result of "some confusion."

"If your life is in jeopardy in the Bahamas... you're going to be allowed into the United States," provided the people arriving are not deemed a threat, he said.

Authorities in the Bahamas have updated the death toll from Hurricane Dorian to 45, one week after the storm battered the archipelago.

Police are calling for the public to register details of the many people still missing.