Scotland Yard confirmed that the Latvian immigrant’s body was found in dense woodland in Boston Manor Park, Hanwell, close to the home Zalkalns shared with his partner and one-year-old child.
The discovery comes just days after Alice’s well-concealed corpse turned up Tuesday in the River Brent, along with her backpack containing her lunchbox, clothes and shoes.
Convicted killer Zalkalns, 41, who had been missing since September 3, was seen on CCTV cycling past the same spot 15 minutes after the 14-year-old girl was last seen walking along the towpath beside the Grand Union Canal near her home.
Zalkans was reported missing by his partner on September 4, one week after Alice's disappearance, when he failed to return home to his flat in Ealing, just a few miles from the schoolgirl's home in Hanwell.
There had been fears that Zalkalns may have fled to his native Latvia, but the Metropolitan Police had not yet been able to apply for a European Arrest Warrant due to lack of evidence.
The police had come under criticism for not identifying Zalkalns as a suspect sooner.
Zalkalns was convicted and jailed in June 1997 after brutally killing his wife and burying her in a forest close to their home in the Latvian capital of Riga.
But he was released from prison two years early after serving just five-and-a-half years, and later travelled to Britain, where he began working as a builder.
The murdered schoolgirl’s autopsy began at Uxbridge Mortuary on Wednesday but lasted until Thursday evening due to the "complex nature" of the investigation, Scotland Yard said.
Following the discovery, police said their investigation into her disappearance had become a murder inquiry.