Thousands of undocumented immigrants will be rounded up for deportation beginning Sunday, reports the New York Times.

Raids will be conducted by Immigration and Customs Enforcement (ICE) over several days in at least 10 cities around the country, the Times says, citing three unnamed sources, identified as one former and two current homeland security officials.

ICE agents will specifically target at least 2,000 people, including many families, but may arrest others for what the sources call “collateral” deportations — “immigrants who happened to be on the scene, even though they were not targets of the raids.”

Most, if not all of those targeted entered the U.S. relatively recently.

“When possible, family members who are arrested together will be held in family detention centers in Texas and Pennsylvania,” the Times says. “But because of space limitations, some might end up staying in hotel rooms until their travel documents can be prepared. ICE’s goal is to deport the families as quickly as possible.”

“Agents have expressed apprehensions about arresting babies and young children … [and] also noted that the operation might have limited success because word has already spread among immigrant communities about how to avoid arrest — namely, by refusing to open the door when an agent approaches one’s home.,” says the Times. “ICE agents are not legally allowed to forcibly enter a home.”

But finding and arresting such immigrants may prove to be the easiest part of the task: defense lawyers will almost certainly seek to reopen the families’ cases, which would delay and possibly prevent their expulsion from the U.S.

An additional complication involves children who are U.S. citizens, with undocumented parents. In such a case, the Times says, “ICE agents will need to wait with the children in a hotel room until a relative in the United States can claim them.”

The raids were originally planned to begin on June 23, but were put off after President Trump tweeted about it, “blindsiding ICE agents whose safety officials feared would be compromised as a result,” the Times says. In addition, officials feared the Trump tweet would cause targeted families to leave the addresses ICE knew about.

The number of migrants targeted by the raids may seem large, but more than 144,000 were detained at the border in May alone — a 13-year high. The numbers have declined since then.

House Speaker Nancy Pelosi addressed the upcoming raids Thursday morning.