Teenagers swimming in the river off of the Walter Bean Trail next to Riverbend Drive spotted her body floating in the water and called police around 4 p.m.
Police were able to identify the body after appealing to the public to for help by releasing a photo of a distinctive tattoo depicting a collection of stars on her abdomen.
"We did receive a number of tips and information in regards to the tattoo that was on her torso," said Sgt. David Reibel.
"Those tips assisted in identifying who the person might be. We then went through [and] contacted the family."
Homicide investigators are looking into her death.
According to a Facebook post by local radio station 91.5 The Beat, she was last heard from on June 27, when she departed for Toronto with an "unknown friend."
She was expected to arrive home by June 29, according to the post.
Reibel stressed her death has not been classified as a homicide yet.
"Right now it's a suspicious death," he said. "We're still looking to find out any information we possibly can from witnesses, [and] people that know Erin."
A autopsy was conducted on Saturday in Hamilton and police are still awaiting the results of further forensic analysis.
The investigation is ongoing and anyone who has information, or may have seen Erin Howlett between June 20 and July 5, is asked to call police at 519-650-8500 ext. 8642 or Crimestoppers at 1-800-222-TIPS.