(CNN) Alejandra Duran was devastated the day she decided it was time to get US passport cards for her children.

It wasn't because they were planning to take a trip abroad.

Instead, the 42-year-old legal assistant in Tucson, Arizona, says she felt her children needed passports to protect themselves while going about their daily lives in the United States.

"I feel uncomfortable and I feel insecure because I have an accent," said Duran, a naturalized US citizen who was born in Mexico.

She says all three of her children live in Arizona and were born in the United States, but she's still scared that if they get pulled over one day, authorities won't believe her and she'll need to prove it.

"With the new administration, that fear is bigger than it used to be before," she said. "I try to explain to my kids, that they have all the rights of citizens, even if they don't have blue eyes, that they're judging them for their color and they have the rights to be here."

Asked about such fears, Immigration and Customs Enforcement spokesman Richard Rocha said in a statement that unfounded rumors are "being spread by those who oppose, or don't understand, immigration enforcement."

"Because of all the inaccuracies being broadcast, ICE understands how difficult it can be for the American public to sift through a multitude of misrepresentations to find the truth," he said. "The facts are: ICE does not conduct indiscriminate 'raids.' ICE officers know their intended targets before setting out to make any at-large arrests. Officers do not randomly ask people for proof of their immigration status. Most people ICE arrests throughout the country are apprehended after being released from a local jail following an arrest for a crime."

A number of US citizens say they are now carrying their passports at all times.

But Duran is not alone in sharing concerns that she and her family could someday be forced to prove they belong in the United States. As the Trump administration has broadened its efforts to crack down on illegal and legal immigration in recent weeks, a number of US citizens have taken to Twitter to share their concerns and talk about their plans to carry their passports.

Joey Reyes started carrying their passport last month while getting a driver's license renewed -- and hasn't stopped.

The 24-year-old theater producer and manager in New York City said the case of a teen in Texas who was held in ICE custody left them shaken.

"It's been so much on my mind lately," Reyes said, "I even woke up from a nightmare where I was being detained."

There's no way to quantify how widespread the practice of US citizens carrying their passports has become. Plenty of Americans are going about their business without carrying passports or other identifying documents. And there's no law stating that US citizens must carry identification with them in their daily lives.

But that anyone feels compelled to do it at all is a troubling sign of the times, said Carlos Guevara, a senior policy adviser on immigration at the advocacy group UnidosUS.

"It's sad to say we're having these types of conversations," he said, "but they're getting more frequent."

Policy shifts are making many people feel more vulnerable

US citizens and immigration experts who spoke with CNN said a number of recent developments are making some people more inclined to carry their documents with them and fueling growing fears among immigrants and US citizens in their families.

"It feels like something's shifting right now, in the past four weeks," Guevara said. Even events and policy changes that aren't directly aimed at them have made US citizens and legal residents feel vulnerable, he said.

Among them:

• The case of 18-year-old Francisco Galicia, which drew national attention in July: The Texas-born teenager ended up in ICE custody for weeks after he and his brother were stopped at a US Customs and Border Protection checkpoint. Authorities said he was held because he had "provided conflicting reports regarding status of citizenship after being apprehended," and noted that "generally, situations including conflicting reports from the individual and multiple birth certificates can, and should, take more time to verify." Advocates claimed the case showed that authorities were overstepping as they stepped up immigration enforcement.

• The administration's efforts to speed up deportations by expanding a process known as expedited removal: Under new guidelines, authorities can swiftly detain and deport undocumented immigrants anywhere in the US who cannot prove they've lived in the US continuously for two years or more. Advocates are challenging it in court. As a result of the policy change, lawyers say some immigrants have already started carrying around things like rent check receipts and tax returns going back years, afraid of run-ins with immigration authorities. "That's a big mental and emotional burden for someone to shoulder, to not be able to leave their house without all this documentation," Chicago-based immigration attorney Fiona McEntee told CNN.

• Trump's widely publicized threats of ICE raids: While the number of people arrested by ICE in an operation last month was far lower than Trump had warned, tthe recent operation where nearly 700 undocumented workers were detained in Mississippi has made more Americans aware of efforts to increase immigration enforcement -- and the impact such enforcement can have on US citizens.

• The administration's new public charge rule: The measure could dramatically cut the number of legal immigrants allowed to enter and stay in the US by making it easier to reject green card and visa applications. Under the rule, many green card and visa applicants could be turned down if they have low incomes or little education and have used benefits such as Medicaid, food stamps and housing vouchers because they'd be deemed more likely to need government assistance in the future.

Advocates say US citizens are increasingly being questioned, too

Concerns about US citizens ending up in immigration detention aren't new.

An investigation by the Los Angeles Times in 2018 found that ICE had released more than 1,400 people from custody since 2012 after investigating citizenship claims.

Matt Albence, now ICE's acting director, said in a statement to the newspaper at the time that the agency takes any assertions that a detained individual may be a US citizen very seriously.

"It is ICE policy to carefully and expeditiously investigate and analyze the potential U.S. citizenship of individuals encountered by ICE," he said.

ICE updates its records when errors are found, he said, and agents arrest only those they have probable cause to suspect are eligible for deportation.

The number of US citizens detained at any point is a fraction of the tens of thousands of people who are held in ICE custody daily. But advocates say even one US citizen detained is too many.

"These errors can have profound consequences, both for the people who are wrongly held and for the state and local agencies that hold them," the American Civil Liberties Union said in a report earlier this year. "As recent cases illustrate, U.S. citizens have been kept in jail away from their jobs and families, and they have faced the terror of being told they would soon be deported from their only home."

A recent analysis by the American Immigration Council, a Washington-based advocacy organization that's suing the government over its recent efforts to fast track deportations, noted that more US citizens are being questioned by ICE, describing it as a "striking change."

"In the first year after President Trump took office, ICE encountered 27,540 U.S. citizens. In comparison, during the last year of the Obama administration ICE encountered 5,940 U.S. citizens," the advocacy group said in a recent report, which it said was based on government statistics obtained through Freedom of Information Act requests.

ICE says the agency isn't able to confirm information released by other organizations or the methodology used for their analysis.

"This trend poses questions about the effectiveness of ICE's enforcement approach and whether certain U.S. citizens who may 'appear deportable' have become increasingly vulnerable to enforcement actions," the American Immigration Council's report says.

That's one more reason why Reyes -- the theater producer in New York -- has been reaching out to immediate family members and advising them to carry passports, too, even though all of them were born in the United States.

"In a sense, I felt like I was overreacting, but another part of me felt like I wasn't. It's just a matter of wanting to make sure that everyone is prepared as much as possible if anything ever happens," Reyes said. "It's something I wish I felt like I didn't need to be prepared for."