Following the pleas of law enforcement officials, the Federal Emergency Management Agency has agreed to cross-check a list of convicted sex offenders against a list of those who registered for federal aid after the Hurricane Katrina disaster, authorities said Thursday.

But local law enforcement officials said the work has still not begun.

Authorities said the cross-checking is important because convicted sex offenders, who might be among the hundreds of thousands of evacuees, must be made to register, in compliance with state and federal laws. Louisiana has provided surrounding states with a list of the 1,340 convicted sex offenders and of the 10,000 parolees who were registered in New Orleans before Katrina hit the city in late August.

Civil liberties groups have opposed wholesale background checks on all evacuees from Katrina-affected regions but have not fought the concept of cross-checking databases for individuals of concern.

On Oct. 13, Vice Adm. Thad W. Allen, the Coast Guard chief of staff leading the federal response to Katrina, told District Attorney Susan D. Reed of Bexar County, Tex., that FEMA will begin cross-checking its database for sex offenders and parolees. "Vice Adm. Allen and his staff immediately recognized the importance of this issue and have moved as fast as possible to correct the situation for the benefit of all concerned," Reed said in a statement. "Their prompt efforts are most appreciated."

The next day, Reed's staff formally requested that FEMA do the cross-checking. On Thursday, they received a reply asking them to reapply, said Cliff Herberg, the first assistant district attorney in Bexar County. "It's like we have to request to make a request. I don't get it," he said.

"We're hearing a lot of pretty words, but nothing is happening," Herberg said. "Basically, FEMA is aiding and abetting these people as they hide from law enforcement."

A FEMA spokesman denied that FEMA is not cooperating.

"We have received the request, we've honored the request and the request is in process," said David Passey, a FEMA spokesman based in Louisiana, referring to the Bexar County request. "We are committed to ensuring that individuals affected by Hurricane Katrina and Rita have a safe place to live."