A grand piano was found overturned inside the trashed apartment home of ex-Olympian Grant Hackett and wife Candice Alley early Sunday morning.

Eight police cars responded to a call about an incident at the celebrity couple's Southbank property in Melbourne, but the two have kept silent of what really happened. Witnesses only saw Alley leaving the apartment carrying one of their twin daughters. Hackett was not around.

Whether a domestic quarrel happened or otherwise, the police are trying to find out.

The singer and TV presenter for Wide World of Sports seemed alright earlier in the day with Alley tweeting of their "fabulous" day together at Derby Day in Flemington, according to Daily Telegraph.

Celebrity DJ Ruby Rose tweeted that the ex-swimmer was in high spirits as host and even strutted on the dancefloor.

After the races, Rose, Hackett and Alley went for the afterparty at The Den at The Atlantic in Crown.

Hackett and Grant were married in 2007 and have twin children. He currently works at Nine Network.