Houston, Texas - These days, Martina Grifaldo begins her mornings by posting a special Facebook message for her immigrant community in Houston.

"May everyone who goes out today make it home safely," Grifaldo writes in Spanish to her 171,000 followers.

The Facebook page, managed with fellow activist Francisco Mendoza, aims to warn migrants where possible raids are happening in real time, using photos and videos submitted by community members.

Since President Donald Trump began his immigration crackdown after returning to power in January, federal authorities have increased their detention of undocumented migrants, asylum seekers, and even those with Latino features who have US citizenship or permanent residency.

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Social media has flooded with pictures and videos of these arrests, some of which turn violent, despite uproar from civil and human rights groups.

Several times a week, Grifaldo (62) goes out on patrol before the crack of dawn to monitor areas where immigration authorities usually operate in Houston, the fourth most populous city in the US and the largest in Texas.

"We start around 5:30 or 6:00 AM with a 'good morning' message, and people send each other blessings. Then we ask: how are the roads?" said Grifaldo, director of the nonprofit Alianza Latina Internacional.

US immigration raids are carried out by ICE agents, with images of frozen water becoming synonymous with migrant detentions.

A common roadside warning sign, "Beware of ice on roads," now carries a double meaning for Latino communities.

"In our posts, we put a picture of an ice cube next to an image of a police officer, and we ask the public to help report" where they are, Grifaldo explained.

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Through their own observations and submissions from followers, Grifaldo and her collaborator Mendoza share information about raids taking place in the city.

On several occasions, ICE agents carrying out raids did not identify themselves, did not wear official uniforms, and did not even show arrest warrants.

This makes Grifaldo and Mendoza suspect that the raids are sometimes carried out by bounty hunters, though federal immigration officials have denied employing such methods.

Even so, it is common for ICE agents to wear masks, military-style vests, and use violence when carrying out raids.

"Every time we go out and check the reports, and we see them, we see how they treat our people, we feel... terrorized, because at any time it could happen to us," said Mendoza (57), head of disaster management at Alianza Latina Internacional.

Grifaldo, who works as a public notary and researcher, volunteers her time to conduct the patrols along with Mendoza, a Mexican immigrant himself who runs an air conditioning and plumbing business.

As Grifaldo and Mendoza drive in their truck, the pair continue to broadcast live on their page.

They later stop for a bite at a fast-food restaurant, invited by local employees in a show of thanks for their work.

"I respect them because they are taking risks for us," said Elizabeth, a 35-year-old woman who works at the restaurant and is seeking legal status in the US. She came to the US from El Salvador more than a decade ago with her mother and son.

"I take care of my mother, who has fallen ill. Imagine if she was waiting for me, and I did not come home," Elizabeth continued.

Mendoza said it was "heartbreaking" how America treats migrants.

"Undocumented people pay so much taxes... and we don't receive anything back," Mendoza told AFP.

Undocumented workers paid $97 billion in taxes in 2022 alone, according to Americans for Tax Fairness.

As Mendoza and Grifaldo conduct their patrols, they inspect work vehicles, such as vans and pickup trucks, that appear to be abandoned, as they can be left behind by migrant workers who have been detained.

By the late afternoon, they wind down their patrol, and Grifaldo pens another message for the Facebook page: "Good night, warriors. Even though it's hard, we have to rest. Tomorrow will be another day to continue resisting."