The RCMP conducted an air search over LaSalle on behalf of the LaSalle Police Service on Wednesday.
LaSalle police continue to look for the person who made in excess of 20 calls to 911 shortly after midnight.
LaSalle Police Service Const. Jamie Nestor said the caller was faint and the person sounded like they were having trouble breathing.
Nestor said the caller also said they were outside and "kept asking for help."
It was impossible to determine the age or gender of the caller because the voice was so faint, he said.
Nestor said police queried the phone number but found it was invalid and no longer subscribed to a user.
"All cellphones, as long as they can work and have a battery in them ... people can still call 911 using those phones. This is one of those cases," Nestor said.
Nestor said dispatchers were able to use GPS technology to determine the call was coming from the area of Morton Drive and Malden Road, an area with thick brush and walking and bike trails.
Police officers on foot, bike and ATVs conducted a search but didn't turn up anything. So, the RCMP were called and is using their plane to search the area from the air.
We are searching for someone who placed several distress 911 calls overnight. Any info please contact us. pic.twitter.com/AuZvyQSC5E— LaSalle Police ON (@LaSallePoliceON) April 30, 2014
Nestor said a hoax "is a possibility."
"We don't want to rule out anything. We don't want to underplay. We're treating it very seriously," Nestor said. "We're doing everything we can to locate a person in case it is an actual, real call."
Nestor wants people in the area to keep an eye open for people in distress in the area. He said to also keep look out for anything like clothes, bags, shoes or phones out of place.
LaSalle police plan to release more information about the investigation on Thursday.