Police have now spoken to the person who they believe was the last person to see Timaru 17-year-old George Hill alive on Saturday night.

Police believe Hill tripped or fell to his death from a roof behind Timaru's CBD and was by himself at the time of the tragedy, Detective Will Joines said.

Hill's body was found in an alley behind Stafford St in the early hours of Monday morning.

Police issued a public plea through Stuff on Tuesday after closed circuit television (CCTV) footage showed Hill and others trying to enter the Sail & Anchor Bar, located not far from where his body was found.

Joines said police have now spoken to everyone of interest that was in the CCTV footage before Hill died, but urged anyone else who spoke to Hill and may not have been in the CCTV footage to come forward.

"If there's anybody else that spoke to George around 12.30am on Sunday then we'd love to hear from them," Joines said.

Joines wouldn't disclose what was discussed with the latest person to come forward, but believes they were the last person to see Hill alive.

"We also spoke to another person on Wednesday night.

"It hasn't really changed how police are looking at things and we're still not treating it as a suspicious death.

"We're still working on timeframes on exactly when certain things happened."

Joines said the other two people spoken to were also with Hill on Saturday night. He wouldn't say whether they were male or female.

Anyone with any information relating to Hill's movements on Saturday night and the early hours of Sunday morning should contact Joines on 021 190 9668.