Reports of an injured child near a canal bridge over the Shropshire Union Canal at Reapers Walk, Pendeford, came through just before 4.15pm on Friday. However, nothing could be done to save him.
West Midlands Police arrested a 16-year-old boy and 46-year-old woman, both from Wolverhampton, in connection with the death.
On Monday morning the force issued an updated about the teenager who had been detained on suspicion of murder.
"A 16-year-old boy remains in custody this morning after a magistrate granted more time for detectives to question him over the death of a 15-year-old boy in Pendeford, Wolverhampton on Friday," a statement said.
"Updates will follow as soon as we have them."
The woman, who was arrested on suspicion of assisting an offender, has been released pending further enquiries.
Officers believe a video showing some of the incident was posted on Snapchat and are appealing for it to be sent to them.
In an appeal launched over the weekend, a police spokesperson said: "We also believe that a video showing some of the incident was posted on Snapchat. The video is vital to our investigation and we’re appealing for anyone with a copy of it to send it in, or let us know which accounts it was shared by.
"Our thoughts remain with the boy’s family and friends whose lives have been forever changed.
"If you have a copy of the video, and need to send it to us you should email the investigation team directly on email@example.com."
Anybody else with information is urged to contact West Midlands Police and quote reference number 2838 of May 27, or Crimestoppers anonymously on 0800 555 111.