Ontario Provincial Police officers are in the water along the St. Lawrence River, searching for a missing diver.
One diver returned to shore on Macdonell Island around 9 a.m., Tuesday, only to discover that his diving partner hadn't surfaced.
The OPP Marine Unit, along with the South Stormont Fire Service, RCMP, Canadian Coast Guard, United States Customs and Border Protection and members of the joint rescue team from CFB Trenton are scouring the water, just west of Cornwall.
The OPP Search and Recovery Unit will be on the scene Wednesday if nothing is found Tuesday.
Police are asking that the public avoid the area while the investigation continues.
Anyone with information on the above is asked to call SD&G OPP at 1-888-310-1122 or Crime Stoppers at 1-800-222-8477.