Police could see the back doors of the lorry moving as the people inside knocked to be let out, the officer in charge of the investigation has said.
Somerset Area Superintendent Geoff Wessell spoke to ITV News:
More top news
Kenyans Eliud Kipchoge and Vivian Cheruiyot won the men's and women's races respectively, in a scorching hot London Marathon.
The King of Pop wore his "magic shoes" when he performed his famous moonwalk on stage for the first time during a rehearsal of Billie Jean.
The body has not been formally identified but officers believe it is 40-year-old Dean Tate, who was reported missing two months ago.