Federal immigration agents rounded up about 26 undocumented people on probation as they showed up in Fort Worth Sunday morning to perform community service.

"I turn back around again and I saw the big coach bus and I said 'dude that's ICE,'" said Hector Rivera, one of the parolees on the bus.

More than two dozen undocumented immigrants are in federal custody after an ICE-led operation in Fort Worth.

It is believed to be one of the largest such sweeps in North Texas in recent memory and perhaps the first of undocumented immigrants who reported for court-ordered community service, like picking up trash along highways.

Those arrested were convicted of high-level misdemeanors or low-level felonies like drunk driving, theft and assault, said Tarrant County Sheriff Bill Waybourn.

An NBC 5 photographer saw an ICE bus and two vans pull up to the Tarrant County Work Release site on Cold Springs Road.

Most of those arrested could be seen being frisked as they were escorted onto the bus. One man was shackled.

"They were really nervous, 'oh my God,' 'oh my kid' and everything," said Rivera. "Some were saying 'oh we got to run.'"

Rivera said the men on board were desperate to get word to their families.

"One of the guys has a pen and we started writing phone numbers, 'hey call my wife,' 'call my dad,' I said 'OK, don't worry, I'll do it.' That's the least I can do," said Rivera.

Juan Herrera's brother Jaime, who has been in the country for nearly a decade and has three U.S.-born children, was arrested Sunday while following a court order.

"It's kind of weird, because the people who don't do it, still outside and the people who try to be straight and pay all the money back and everything, that's what happened," said Herrera.

ICE spokesman Carl Rusnock confirmed the operation, but declined to immediately provide any details.

"ICE officers are conducting ongoing immigration enforcement operations in North Texas," he said in an email. "No further details are available until the conclusion of this operation. ICE routinely conducts immigration enforcement operations locally and nationwide which help improve overall public safety by removing criminal aliens from our communities."

Waybourn said his office participated in the operation at ICE's request.

"This was totally initiated by ICE," he said. "They came to us and said, 'Listen, we reviewed the list (of names) and we suspect some of them are illegal aliens.' So we said, 'Whatever you need to do.'"

Waybourn said the families of those arrested had been notified.

Those arrested were taken to an ICE facility in Dallas where they will be processed and some possibly released, he said.

Waybourn campaigned on cracking down on undocumented immigrants, especially those convicted of crimes.

Soon after he took office in January, he applied to take part in a federal program that would train jailers to enforce immigration laws.

Immigration attorney Jaime Barron says the legal outcomes for the men will vary.

"It's just going to be a mixed bag, some people probably will find relief in the immigration court and some others might be forced to be deported," Barron said.

On Monday, family members showed up at ICE headquarters in Dallas to ask about their loved ones.

"Yeah I'm upset because I don't feel this is right," said Erica Savillon.

She married her husband Andy in December and he is still undocumented, she said.

He is from Honduras. She is American.

Erica Savillon said it's not fair her husband was rounded up when he was performing community service for a drunk driving conviction.

"I get it, if you do something wrong, pay for what you did," she said. "But he's trying to pay for that and he still gets taken away."

Activists said at least several of those detained could be released on bond as early as Tuesday, including Erica Savillon's husband.