Aurora Mayor Mike Coffman, whose city became associated with illegal immigration issues this past election season, wrote in an op-ed Monday that Denver Mayor Mike Johnston placed migrants from the Colorado capital in his city.

Coffman said he learned through a City Journal report that Johnston was using two nonprofits to house migrants.

“After reading the article, I confronted Johnston about whether this was true. He affirmed that Denver had contracts with nonprofits that ‘have’ placed migrants from Denver to Aurora but he refused to confirm a number, where they were housed, or what resources they were given,” Coffman said. “He defensively said that information wasn’t available.”

The City Journal report discusses how the two nonprofits were working with landlords to place migrants in units and to subsidize their rent. Contracts between the organizations and Denver included the words “in Denver or in the surrounding communities,” according to Coffman, who claimed they were inserted “quietly.”

“It gives Johnston cover, should it become public, by allowing him to say that it wasn’t his decision to put them in Aurora; it was the nonprofits who made the decision,” the op-ed reads.

A provision in the contracts requires the nonprofits to disclose how many migrants were placed in Aurora, as well as where in the city they were housed, Coffman noted. Denver City Attorney Kerry Tipper has said that information cannot be released since it contains details that identify the migrants, according to the Aurora mayor.

“Then, Denver should redact the names and send us the information,” Coffman wrote.

He asked Johnston to “be transparent and tell the truth about what he did.”

“Aurora has suffered from a national embarrassment that has harmed the image of our city in a way that could have lasting economic consequences,” the op-ed continues.

Johnston’s office did not immediately respond to a request for comment.