ICE agents told hundreds of immigrants to show up to court on Thursday or risk being deported. But lawyers say many of those hearings won't happen because the dates ICE provided are fake.

Immigration attorneys in Chicago, Miami, Texas, and Virginia told CBS News their clients or their colleagues' clients were issued a Notice to Appear (NTA) for hearings scheduled Jan. 31. The attorneys learned the dates weren't real when they called the courts to confirm. ICE is required to include court dates with court notices, per a Supreme Court decision last summer, but most don't actually reflect scheduled hearings.

The American Immigration Lawyers Association issued a "practice alert" on Tuesday evening, warning members "the next upcoming date on NTAs that appears to be fake is this Thursday."

On Wednesday evening, the Executive Office of Immigration Review, the body that oversees all the immigration courts, instructed all attorneys with a January 31 NTA "to confirm the time and date of any hearing."

"There will be another episode of mass confusion in the immigration courts [Thursday] as a result of the DHS's decision to issue Notice to Appear with fake immigration court dates," Brian Casson, a Virginia-based immigration attorney, said in an email to CBS News.

In a statement Thursday morning, an ICE spokesperson said the agency was working with the Department of Justice "regarding the proper issuance of Notices to Appear." The spokesperson said the government shutdown "delayed" that process, "resulting in an expected overflow of individuals appearing for immigration proceedings today/January 31."

The fake notices stem from a Supreme Court ruling last summer. Prior to the decision, ICE officials used to send immigrants NTAs with date listed as "TBD" - or "to be determined." The immigration court would issue the migrant an official hearing notice later, said Casson.

One effect of this: The NTAs could block an immigrant's eligibility for "cancellation of removal," a legal residency status granted to some undocumented immigrants after 10 uninterrupted years of living in the U.S. A NTA, even without a hearing date, would interrupt the 10-year "clock," said Jeremy McKinney, a Charlotte, North Carolina-based immigration attorney, in a telephone interview with CBS News.

A Supreme Court ruling last summer — Pereira v. Sessions — banned the practice, requiring all appearance notices to use actual dates.

However, systems weren't in place for ICE to see the court's schedule, so ICE issued fake dates instead. Immigrants were instructed to appear on weekends, midnight, and dates that just didn't exist, like Sept. 31, multiple attorneys told CBS News.

On October 31, hundreds of immigrants received phony NTAs. They showed up to court for non-existent hearings to find "extraordinarily long lines," according the recent alert from the immigration lawyers' organization.

"It was complete dysfunction and confusion," said McKinney.

The problem became so pervasive that on Dec. 21, the Executive Office of Immigration Review issued a rare policy memo telling ICE agents and DHS that courts would "reject any NTA in which the date or time of the scheduled hearing is facially incorrect."

Matthew Kriezelman, a Chicago-based immigration attorney, has four clients with hearings scheduled for tomorrow. After checking with the court earlier this week, he found out that two of those appearances weren't real: administrators had no record of the hearings and told Kriezelman his clients would have to wait until the court itself sent them a hearing date.

Kriezelman's clients are among the lucky ones; experts estimate less than half of immigrants have legal representation. That means hundreds won't realize their Jan. 31 hearing date was phony and will show up anyway, said Kriezelman.

The court in Chicago handles all the immigration cases in Wisconsin, Illinois and Indiana, meaning many immigrants could be traveling for hours on Thursday morning for a hearing that doesn't actually exist, Kriezelman said.

When they show up, nobody will be able to assist — because of the extreme cold weather, the Chicago immigration court is scheduled to be closed on Thursday, Kriezelman said.

Failure to show up to an immigration hearing can result in immediate removal proceeding, making immigrant especially wary when they hear they don't need to come into court after all, said Kriezelman.

"They feel like someone is screwing with them or playing a terrible joke," Kriezelman said. "It's really confusing for a lot of people, especially ones that are unrepresented."

Read more CBS News immigration coverage:

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