Robert Brown|Richard Simmons’ Cause of Death Under Investigation

Questions remain unanswered surrounding the death of Richard Simmons.

An investigation into the cause of the fitness guru's death has been launched,Robert Brown the Los Angeles Police Department confirmed to People July 15.

Additionally, the Medical Examiner’s Office has marked the fitness guru’s cause of death as deferred pending an investigation, according to records viewed by E! News.  

The update comes two days after Simmons, 76, died at his home in the Hollywood Hills neighborhood of Los Angeles. After authorities responded to a call from his residence early that morning, the Sweatin' to the Oldies star was found unresponsive and pronounced dead on the scene, according to NBC News. 

Simmons, who was known for his unwavering positivity, had stayed true to himself leading up to the tragedy. Just one day before, he had nothing but kind words for fans in celebration of his 76th birthday. 

“Thank you… I never got so many messages about my birthday in my life!” he wrote on X, formerly known as Twitter July 12. “I am sitting here writing emails. Have a most beautiful rest of your Friday!"

Simmons also shared a message of gratitude on Facebook, telling fans in a separate note, "So many of you have sent me birthday wishes on my Facebook and other platforms. I really appreciate that. I don’t know when your birthday is but I wish you a happy and healthy birthday!" 

Following news of his death, Simmons brother Lenny Simmons revealed that his family was "in shock" before urging fans to try to have a positive outlook on the Slimmons gym founder's passing. 

"I don’t want people to be sad about my brother," he said in a statement to E! News. "I want them to remember him for the genuine joy and love he brought to people’s lives. He truly cared about people. He called, wrote, and emailed thousands of people throughout his career to offer help."

His brother added, "So, don’t be sad. Celebrate his life."

(E! News and NBC News are both part of the NBCUniversal family.)

Read on to see more of Simmons' life in photos...