The fight between short-term rental platform Airbnb and New York City is intensifying, with Mayor Bill de Blasio demanding the site hand over its listing data.

“We want to see their listings. We want to see which apartments are being rented out. We want to know what’s really going on,” de Blasio said on NY1 this week. The city is issuing Airbnb with a subpoena for the information, Housing Wire reports.

“We want to make sure there’s not illegal hotels," de Blasio said. "We want to make sure that something that is supposed to be an occasional business is not a full-time business, which would mean it should be listed as a business … It should be regulated as a business."

A law passed in 2016 prevents homes being rented out for fewer than 30 days, and the city is trying to bring in a law that would force short-term rentals like Airbnb to provide listing information to authorities.

However, Airbnb sued the city and in January a federal judge blocked the law — finding that the companies would likely win in their claim that the law was unconstitutional as it could run up against Fourth Amendment protections against illegal search and seizure.

The law was due to come into effect this month, but wasn’t able to move ahead the further litigation is resolved.

Critics of Airbnb say that it worsens the city’s housing affordability problems, but Airbnb Head of Global Policy Chris Lehane wrote in a letter to the mayor that the company has “offered to work with the City to collaboratively focus enforcement efforts on weeding out large-scale commercial operators who seek to circumvent our policies."

"And while that offer hasn’t yet been accepted, we stand by it," he wrote.