Donald Trump says the United States will have to be careful about accepting Bahamian survivors of Hurricane Dorian, warning there could be "very bad people" among them.

Key points: Mr Trump said he did not want to allow "people that weren't supposed to be in the Bahamas to come into the United States"

Mr Trump said he did not want to allow "people that weren't supposed to be in the Bahamas to come into the United States" Storm survivors were prevented from boarding a ferry from the Bahamas to Florida because they lacked US visas

Storm survivors were prevented from boarding a ferry from the Bahamas to Florida because they lacked US visas Mr Trump said everyone needed "proper documentation" to enter the country

The day before the United States President made the comments, several hundred storm survivors were prevented from boarding a ferry to Florida because they lacked US visas, in what authorities have labelled a mistake.

Forty-five people are now known to have died when the giant storm battered the archipelago with winds of 295 kilometres per hour one week ago, but the search for victims and survivors is continuing, and authorities say they fear the death toll will rise.

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

"The Bahamas has some tremendous problems with people going to the Bahamas that weren't supposed to be there," Mr 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, Mr Trump has made multiple efforts to stem the inflow of migrants, mainly from Central America, and previously made similar statements about immigrants from Mexico, suggesting they were "rapists" who would bring "drugs" and "crime".

Survivors have been evacuating the Bahamas via ferry. ( Reuters: Marco Bello )

Bahamians currently need a visa to travel to the US unless they are pre-screened by US customs officers at one of the two main Bahamian airports.

However, storm victims have been allowed to evacuate to the US providing they are able to show a passport and proof of no criminal record, prompting US Customs to blame Sunday's incident on the ferry operator.

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

Authorities in the Bahamas have updated the death toll to 45. ( AP: Gonzalo Gaudenzi )

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

Dorian bought devastation to parts of the Bahamas, destroying houses and swamping others in its storm surge.

US Agency for International Development head Mark Green said he was "struck by the focused nature of the devastation" on the Abacos Islands, saying some areas looked "almost as though a nuclear bomb was dropped".

Search and rescue teams are still trying to reach some northern Bahamian communities isolated by floodwaters and debris.

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

AFP/Reuters/AP