Two U.S. senators are seeking a congressional probe into the risk of money laundering in the real-estate sector.

Sens. Chris Van Hollen of Maryland and Sheldon Whitehouse of Rhode Island, both Democrats, sent a letter Wednesday to Gene Dodaro, head of the Government Accountability Office, seeking assistance with an investigation into vulnerabilities in the U.S. anti-money-laundering legal regime related to the real-estate sector.

“Residential...