Mississippi ? Nearly 6,000 residents in Mississippi, Louisiana and Alabama face a May 1 deadline to leave the government trailers where they have lived since Hurricanes Katrina and Rita raked the Gulf Coast.

The Federal Emergency Management Agency said the $5.6 billion housing assistance program that began after the 2005 storms was the largest federal temporary housing operation in the nation’s history.

At its peak, 143,000 households along the Gulf Coast were living in temporary housing units.

FEMA is urging its remaining tenants in travel trailers to work with federal and state case managers up to the deadline to find permanent housing. Those living in park model or larger homes have the option to purchase the structures.

Otherwise, FEMA spokesman Jim Foster said, on May 1, “they will have to move out. That’s just the end of the program.”

Advocacy groups, many of them established in Katrina’s wake, have been scrambling to help people who haven’t found permanent housing. Many displaced residents are over 65 or are disabled, said Stephen Carr, director of the Mississippi Case Management Program.

The main barrier is affordability. Following Katrina, rent more than doubled along the Mississippi Gulf Coast. Much of the affordable housing stock was destroyed and insurance rates increased. Hundreds of housing units have been replaced within the last year, but “developers can’t put it on line at pre-Katrina rates,” Carr said.

The state also plans to transform 1,800 so-called Katrina Cottages — billed as a sturdier alternative to trailers — into permanent structures. The cottages, which are state structures, are not affected by the FEMA deadline.