A government crackdown on illegal immigration (search) in southern Arizona will continue beyond Sept. 30, the day the initiative was supposed to wrap up, a top Homeland Security official said Tuesday.

Some agents, prosecutors and helicopters that had been transferred to Arizona for the crackdown will remain permanently, said Asa Hutchinson, undersecretary for border and transportation security.

The buildup, which began in March, aimed at clamping down on the soaring numbers of illegal immigrants brought into Arizona by smugglers from Mexico.

The action has resulted in more than 351,700 apprehensions of illegal immigrants on the Arizona border, compared with about 225,000 during the same period in the 2003 fiscal year, Hutchinson said.

"I'm not here today saying we've fixed a problem. I'm saying that we've made progress on a problem, and we're devoting resources and a great deal of attention and effort to it," he said.

The initiative included an additional 200 seasoned Border Patrol (searchagents permanently reassigned to the agency's Tucson sector, which in recent years has become the nation's busiest region for illegal border crossings from Mexico.

More than 2,100 agents are now assigned to the sector, which covers all the Arizona-Mexico border except an area around Yuma, sector Chief Michael Nicley said.

The government will also briefly extend a voluntary program that offered free flights to the Mexican interior for illegal immigrants caught while crossing the border into Arizona.

Since July 12, some 12,000 people have been flown to Mexico City and Guadalajara. More than half were volunteers, and the rest were deemed at physical risk if they tried to cross the desert again, Nicley said.

"Initial indications are that it was a successful program, but we want to evaluate it further," Hutchinson said.

He said he would like to see the repatriation program continued and made mandatory, but that would have to be negotiated with the Mexican government.