Responding to criticism of secrecy within the immigration detention system, federal officials launched an online service Friday to help relatives and attorneys find detainees in the sprawling networks of prisons and jails.

In the past, locating a relative was cumbersome, time-consuming and sometimes impossible, requiring numerous phone calls to detention centers around the nation.

The public, Internet-based tool is designed to fix that, said Phyllis Coven, acting director of detention policy and planning for U.S. Immigration and Customs Enforcement. The locator can be found at www.ice.gov.

"This is about accountability and transparency," she said. "It is a project that has been needed for a long time."

Ahilan Arulanantham, who directs the immigrant rights and national security program for the ACLU of Southern California, said he was cautiously optimistic about the effort.

"We are hopeful, but our biggest concern is that the system is only good enough as the information that is put in it," he said. "We know that ICE does transfer people very quickly. It is up to them to ensure that the system continues to capture that information."

Around the nation, more than 250 jails, prisons and centers hold on average more than 30,000 immigration violators. Some are awaiting deportation while others are fighting their cases in court. Detainees are frequently transferred around the country.

Los Angeles immigration attorney Luis Ayala said the agency is "trying to alleviate the angst and anxiety" by telling families where their loved ones are being held. But Ayala said that the agency should keep individuals close to their families and lawyers.

"The fact that they are launching this is good, but the best remedy would be to not transfer them," he said.

The tool is part of a broader effort to transform the system from a prison-based model to one designed for civil detainees. "The premise is making our detention centers less penal and more tailored to the purpose of our confinement, which is the purpose of removal," Coven said.

Following media reports and congressional hearings about inadequate healthcare and deaths in detention, ICE chief John Morton last summer announced a plan to overhaul the detention system.

Since then, among other changes, the agency has stopped detaining certain asylum seekers, conducted a review of its medical program and begun a pilot intake system to better decide who should be detained and where. Coven said the agency is also working on reducing transfers and improving access to counsel.

To find a detainee, the searcher must type in the person's country of origin and either their full name or alien registration number - a unique nine-digit number given to anyone who applies for immigration benefits or in deportation proceedings. With that information, the computer will show the detainee's location, along with contact and visiting information of the center and the local immigration enforcement office.

Coven said the agency is getting out the word about the program through community organizations, immigration field offices and the media. Brochures that explain how to use the system are available in nine languages, including Mandarin, Russian, Somali and Spanish.