Two weeks ago, the number of illegals detained nationwide surpassed 30,000 while California alone had 4,000, the Los Angeles Times reported Monday.

Immigration officials said detention is the only way to guarantee that people leave the country when deportation has been ordered.

"If we have them detained and they are ordered removed, it's almost a virtual certainty that they will, in fact, be removed," Gary Mead, assistant director of the immigration agency's Detention and Removal Operations, told the Times.

Immigrants and their advocates said the rising number of detainees has led to crowded conditions and limited access to medical care for some detainees, the newspaper reported.

In July, the Government Accountability Office reported that populations at four facilities, including San Pedro on Terminal Island and a center in San Diego, were over capacity.

One possibility for dealing with overcrowding is to contract with private facilities since the immigration agency said it has no plans to build more of its own detention centers, the Times' report said.