The DHS notified Congress in late July that it intended to reprogramme funds from several agencies, including the Federal Emergency Management Agency (FEMA), the Transportation Security Administration (TSA) and US Coast Guard - to detention centres managed by Immigration and Customs Enforcement (ICE), said US media reports.
Officials say the motive behind the decision was to bolster President Donald Trump's immigration and border strategy.
A sum of $116 million will be earmarked to increase the number of adult beds in detention centres, the DHS said in a statement.
Currently, the ICE has around 55,000 people in its custody, according to reports, most of them adults who recently arrived in the US and committed no other offence than crossing the border illegally.
The $155 million will serve to "establish and operate temporary (...) immigration hearing facilities along the southwest border", for the Migrant Protection Policy commonly referred to as the "Remain in Mexico" policy under which the US sends migrants back to the neighbouring country while their cases are resolved.
The funnelling of $155 million from FEMA coincides with the US hurricane season and the passage of tropical storm Dorian's through the island of Puerto Rico, which was affected by cyclones Maria and Irma in 2017.
FEMA said that based on a review of its historical emergency spending, the agency will be left with an amount "sufficient to support operational needs and will not impact ongoing long-term recovery efforts across the country" despite the transfer.
The transfer of funds by the DHS, which was originally approved by Congress, was criticized by the Democratic Party.
"The Trump administration's plan to divert money away from FEMA at the start of hurricane season to continue its efforts to separate and jail migrant families is backwards and cruel," Senate Minority Leader Chuck Schumer said on Twitter.
"Taking these critical funds from disaster preparedness and recovery efforts threatens lives and weakens the government's ability to help Americans in the wake of natural disasters," he added.
FEMA has an annual budget of more than $18 billion.
( With inputs from IANS )