The Securities and Exchange Commission has begun a formal investigation into Sunrise Senior Living Inc., the assisted living chain said Tuesday.

The SEC is specifically examining possible insider stock sales, the timing of stock option grants and matters related to Sunrise’s historical accounting practices.

Sunrise last year appointed an independent committee to investigate allegations of financial wrongdoing. The company acted after the Service Employees International Union raised concerns about the failure of the company to publish quarterly earnings statements for 2006. Sunrise has still not disclosed quarterly earnings from last year, and has not yet restated earnings from previous years, as it has intended.