(CBS News) -- The federal budget cuts expected to take effect this Friday are not simple. For example, hundreds of illegal immigrants are being released from detention because the administration says it can't afford to keep them.
Until recently, Fredi Alcazar was one of those detained. An illegal immigrant from Mexico, Alcazar spent a month in jail after a traffic stop near Atlanta last December. He now wears an electronic monitoring band on his ankle. The device lets immigration officials know where he is at all times.
(watch: Releasing illegal immigrants over budget cuts, below)
Alcazar was released unexpectedly in January.
"I was surprised they released me," Alcazar recalled. "They didn't say anything."
Officials at Immigration and Customs Enforcement (ICE) would not tell CBS exactly how many detainees they released ahead of for Friday's automatic budget cuts. They also declined to say where or when the releases occurred.
Those let go, like Fredi Alcazar, are required to wear electronic tracking devices, regularly call immigration officials or visit ICE offices.
"We started getting calls all of a sudden they had been released," said immigration advocate Dulce Guerrero. "We were very much in shock."
The early release of detainees was a surprise to Guerrero.
"These folks are no criminals," she said. "These folks in there are moms, dads, students, community members who are in there for no license, for a broken tail light."
But some members of Congress are demanding ICE provide information on each detainee's case.
"When you release these people and expect them to show up at a court proceeding at a later date, we found before that 90 percent of them don't show up," said Congressman Michael McCaul, chair of the House Homeland Security Committee.Besides Georgia, CBS did learn that many releases were in Arizona, California and Florida. Immigration advocates said that "supervised release" costs about $14 a day compared to about $160 a day to keep detainees in jail.