Police say the post-mortem, will be held at 1.30pm.
The body of a man , which has yet to be formally identified, was discovered in an area of dense woodland in Boston Manor Park, west London, on Saturday afternoon.
Unconfirmed reports say the badly-decomposed body was found hanged.
Alice, 14, from Hanwell, west London, disappeared on 28 August. Her body was found in the River Brent on Tuesday.
However, police believe the body to be that of Zalkans. A spokesman said, "Although no formal identification has been made, early indications suggest the body may be that of Arnis Zalkalns."
The Latvian builder was last seen at his home in Ealing on 3 September, six days after Alice vanished while walking along the Grand Union Canal in west London.
He was filmed on CCTV cycling along the same route just minutes behind the schoolgirl on the day she disappeared.
