Since the 2008 financial crisis, wealthy buyers swooping in and paying cash–sometimes anonymously–have become the bane of traditional homebuyers. Now the Treasury Department says it wants to know if some of those luxury buyers are laundering money through their purchases.

The department’s Financial Crimes Enforcement Network will require title insurance companies that help facilitate such deals to identify the people behind all-cash purchase of high-end homes in Manhattan and Miami-Dade County, Fla. The temporary order intends to pierce the confidentiality often sought by luxury buyers who rely on shell companies or limited liability companies to shield their identity.

The requirement will make it easier to identify people attempting to hide their assets or launder money, Treasury said in a statement.

“We are seeking to understand the risk that corrupt foreign officials, or transnational criminals, may be using premium U.S. real estate to secretly invest millions in dirty money,” Jennifer Shasky Calvery, the director of the Financial Crimes Enforcement Network, said in a statement.

Cash purchases currently comprise more than 20 percent of home purchases nationally, according to the National Association of Realtors. That is down from a peak of 33 percent in late 2013, but still up significantly from the traditional 10 percent. Over the same time, the luxury market, sales of $1 million or more, has stayed steady at about 2 percent of the market, according to industry group.

But cash purchases are a disproportionate part of the market in Miami and New York. In Miami, all-cash deals were more than 50 percent of the sales as of November, according to the Miami Association of Realtors. “Miami’s high percentage of cash sales reflects South Florida’s ability to attract a diverse number of international home buyers, who tend to purchase properties in all cash,” the local association said last month.

“Cash purchases present a more complex gap [in identifying money laundering] that we seek to address,” Calvery said.

The department’s action comes after multiple stories in The New York Times  that examined the use of shell companies by foreign buyers. It’s order is fairly limited. It will be in effect for 180 days beginning in March and only covers sales in Manhattan and Miami-Dade County.

While it doesn’t plug a loophole left in the 2001 Patriot Act, which exempted real estate brokers from rules requiring evidence of potential money laundering to be reported to the government, it could be a first step, said Heather Lowe, legal counsel of the Global Financial Integrity, a D.C.-based research group. “I am certainly encouraged that they’re looking at this. I suspect this could be a vehicle” for further action, Lowe said. “It doesn’t make sense to me otherwise.”

Without additional action, someone attempting to hide their identity or launder money could simply wait until the order expires in August, buy property in another part of the country or simply not use a title company as part of the transaction, she said. “There are a lot of place in the U.S. where I can buy a luxury home” and avoid the department’s reporting requirement, Lowe said.