Two civil liberties groups have filed a lawsuit against the US Department of Homeland Security, complaining that the agency's Customs and Border Protection (CBP) division has routinely searched many US citizens' laptops and other electronic devices and questioned them about their religious practices and political beliefs.

The lawsuit, filed by the Electronic Frontier Foundation (EFF) and the Asian Law Caucus Thursday, asks a federal judge to force CBP to comply with an information request, filed by the two groups on October 31. The two groups filed a Freedom of Information Act request asking CBP to detail its policies for searching laptops, MP3 players, mobile phones, digital cameras and other electronic devices. The two groups also sought information about CBP's policy on questioning travelers about political views, religious practices and other activities "potentially covered by the First Amendment" to the US Constitution, which guarantees freedom of religion and speech.

The two groups also wanted the CBP to explain its policy for responding to a traveler who refused to answer questions and its policy for allowing a detained traveler to contact a lawyer.

Many residents of Northern California have reported that "CBP officials have subjected them to lengthy and intrusive questioning upon their return to the United States," the complaint says. "Individuals who protest such questioning or searches have been told that they have no choice but to cooperate as they are at an international border."

In one case, Nabila Mango, a US citizen coming home from the Middle East, was asked by customs agents at San Francisco International Airport to name every person she had met and every place she had slept during her trip, according to a news release from the civil liberties groups. Agents searched her Arabic music books, business cards and mobile phone, the groups said.

Another US citizen, IT consultant Amir Khan, has been stopped multiple times when returning to the US, the groups said. He's been questioned for hours, and customs agents have searched his laptop, personal notebooks and mobile phone, the groups said.

CBP officials have asked US-based travelers about their families, volunteer activities and educational backgrounds, the complaint says. In addition, they've demanded to see files on laptops, browser histories, mobile phone directories, personal photographs, business cards and other personal materials, according to the complaint.

US residents have a right to know the government's standards for border searches, said Marcia Hofmann, an EFF staff attorney. "Laptops, phones, and other gadgets include vast amounts of personal information," she said in a statement. "When will agents read your e-mail? When do they copy data, where is it stored, and for how long? How will this information follow you throughout your life?"

A CBP spokeswoman didn't immediately respond to a request for a comment on the lawsuit.