Federal agents raided about 20 Southern California locations on Tuesday suspected of involvement in "maternity tourism" schemes offering travel and lodging services to pregnant foreign women seeking to give birth in the United States, US immigration officials said.

Authorities say the so-called maternity hotels targeted in the sweep catered largely to women from China who paid $15,000 to $50,000, depending on services provided, in hopes of obtaining US citizenship for their children.

The locations searched included apartment complexes and other sites in Los Angeles, Orange and San Bernardino counties that were suspected of housing foreign clients, according to a statement issued by the US Immigration and Customs Enforcement Agency, or ICE.

No criminal arrests were anticipated from Tuesday's raids, which were carried out by federal agents and local law enforcement, the agency said.

The US Constitution grants citizenship to any child born on U.S. soil, regardless of parentage, and immigration experts say there was nothing inherently illegal about foreigners giving birth in the US.

But investigators are seeking evidence related to such possible criminal offenses as visa and tax fraud, money laundering and conspiracy, immigration officials said.

Any women encountered at the locations raided on Wednesday were to be interviewed, and potential material witnesses will be instructed where and when to report for further questioning, ICE said.

Businesses engaged in maternity tourism, also known as "birth tourism," are believed to have been operating for several years, relying on websites, newspaper advertising and social media to promote their services, immigration officials said.

Based on the results of previous investigations, the women who subscribe apparently pay cash for pre-natal medical treatment and actual delivery of their babies.

As part of the package, clients were promised they would receive Social Security numbers and US passports for their infants - documentation the mothers would take with them when they returned to their home countries, ICE said.

Once the children, who by birth are US citizens, reach adulthood they can apply for visas for family members living abroad.

More expensive packages "include recreational activities, such as visits to Disneyland, shopping malls and even an outing to a firing range," the ICE statement said.

The practices came to public attention in California in recent years when residents of some Los Angeles-area communities complained about what they said were maternity hotels springing up in their neighborhoods, causing sanitation and other issues.

Reuters