The Securities and Exchange Commission is scrutinizing how Invitation Homes, a subsidiary of Blackstone Group and one of the country’s largest home rental companies, valued assets it sold into mortgage-backed bonds.

Regulators have asked the landlord to provide documentation related to its use of broker's price opinion, the home valuation process that helped companies like Invitation build large portfolios of single-family rentals after the financial crisis, according to International Financing Review. Broker's price opinion are not as in-depth as traditional property appraisals.

Starwood Waypoint Homes, currently in the midst of a merger with Invitation that would create the largest rental-home landlord in the country, has also received a subpoena requesting documentation and communications related to securitizations, SNL reports.

After the financial crisis, a number of companies used broker's price opinion to quickly acquire and bundle portfolios of hundreds of single-family rental home properties into single-family rental bonds. Those bonds are now being investigated to see if they employed the same relaxed standards that contributed to the last housing crisis.

According to IFR, Starwood has put its latest SFR bond offering on hold while the SEC probe is underway.