Federal immigration agents have been busy in Santa Fe this month, taking into custody at least 45 people since late May.

On Memorial Day, agents arrested six immigrants, including two criminal aliens, said Leticia Zamarripa, spokeswoman for the Immigration and Customs Enforcement agency.

During the remainder of that week, agents involved in operations that targeted criminals arrested another 23 people who were in the country illegally, she said.

On Thursday, at an anti-DWI sobriety checkpoint at Interstate 25 and N.M. 599, 16 Mexican citizens were detained as they attempted to pass through the checkpoint in a Ford F150 pickup.

It is unclear who let immigration agents know about the checkpoint or the 16 Mexicans. The Santa Fe County Sheriff's Department, which helped operate the checkpoint, said it did not contact ICE. ICE agents were nearby the checkpoint, however.

While ICE agents were in a position close to the checkpoint, they had tried to get closer, according to state police.

"When they contacted us — state police — we told them they couldn't be at the checkpoint with us," said Peter Olson, spokesman for the New Mexico Department of Public Safety.

"We specifically asked them not to park their vehicles at our checkpoint," he said. "The purpose of these checkpoints are for sobriety, not immigration status, and that's why we asked them to separate from us."

Zamarripa said ICE officials remained near the checkpoint "to be able to respond quickly to state police." She said vehicles packed with many passengers often present safety hazards.

Vehicles being stopped with numerous immigrants inside isn't unheard of, officials say.

Santa Fe County Sheriff's Sgt. Joe McLaughlin said during a checkpoint last November at the I-25 site of a fatal DWI crash that occurred a year earlier south of Santa Fe, deputies encountered another load of undocumented people. He said he couldn't close his eyes to it so he called ICE, they sent agents and while they were taking the aliens into custody, another group came through the checkpoint. Combined, the two groups amounted to more than 20 people.

Although several community members have recently complained ICE staff members haven't identified themselves as immigration officials, Zamarripa said the agents always wear blue jackets bearing the words "ICE Police."

Jason Auslander contributed to this report.

Contact Kate Nash at 986-3036 or knash@sfnewmexican.com. Read her blog, Green Chile Chatter, at www.sfnewmexican.com.

Correction: An earlier version of this story mistakenly reported that the Santa Fe County Sheriff's Department contacted immigration officials. In fact, the Department said it didn't contact ICE and isn't sure who did.