BOSTON -- Agents for the Department of Homeland Security completed a two-day crime sweep in Boston Thursday that placed nearly 60 illegal aliens with criminal records behind bars.

NewsCenter 5's David Boeri reported that Tuesday and Wednesday's operation targeted an area that Boston police call the red zone because of its density of crime.

The sweep was the first operation of this scale targeting so-called "criminal aliens," carried out by agents with Immigration and Customs Enforcement, or ICE.

"We went out, we identified these individuals, we put this operation together and removed 60 violent criminals from our streets," said ICE Special Agent In-Charge Mattthew Etre.

Fifty-seven of those arrested are categorized as "criminal aliens," 43 of those are permanent residents of the United States and 14 are illegal aliens and in the country illegally.

The majority of those arrested, so-called criminal aliens, can be deported on the basis of their prior criminal convictions.

"As they are brought to our attention, we identify these individuals, we process them and deport them from our nation," Etre said.

The problem, officials said, has been identifying the criminals who are in the United States illegally or can be deported.

"Unfortunately, we're dealing with individuals that don't always tell us exactly who they are," said Middlesex County Sheriff James DiPaola.

Identifying those criminal aliens has been a challenge for ICE, which used the arrests to publicize its first big rollout in three years of operation. The operation targets people with a criminal past who are in the country illegally.

"Keying in on, which is a credit to ICE, keying in on those individuals that have criminal convictions that are here in this country illegally, as opposed to someone who is here illegally and being law-abiding citizens," DiPaola said.

By virtue of the police red zone's location -- Dorchester, East Boston, Mattapan and Roxbury -- the great majority of those arrested are black and Hispanic.

The next step in ICE's process is to start deportation proceedings against the aliens that officials want to send back. Those arrested are from 21 different countries.