San Francisco, June 24 (IANS): The US Navy is preparing to build detention centres for tens of thousands of migrants in California, Alabama and Arizona as part of President Donald Trump's "zero tolerance" policy for people caught crossing the southern border illegally.

According to a copy of a draft memo, the plan includes a facility that could house as many as 47,000 people at Camp Pendleton, San Diego County, in Southern California, and another camp for as many people at former Naval Weapons Station Concord, near San Francisco, Xinhua news agency reported on Sunday.

The memo outlines plans to build "temporary and austere" tent cities to house 25,000 migrants at abandoned airfields just outside the Florida panhandle near Mobile, Alabama, at Navy Outlying Field Wolf in Orange Beach, Alabama, and near Navy Outlying Field Silverhill.

It also proposes further study on housing an undetermined number of migrants at the Marine Corps Air Station near Yuma, Arizona.

The navy would spend about $233 million to construct and operate a facility for 25,000 people for a six-month time period.

The document, prepared by an assistant secretary for Navy Secretary Richard Spencer's approval, suggests construction could begin within 60 days.

Trump, facing domestic and international backlash, signed an executive order last week to end the administration's controversial practice of separating migrant children from parents crossing the US border illegally.