Chris Vilela, a traffic watcher who compiles reports on road conditions in the Kingston area and shares them via social media, said weather and road conditions have been getting worse in the region all day.
"The roads are absolutely terrible," he told CBC News. "The conditions are perfect for black ice."
Vilela said he's seen reports of blowing snow in the area around Napanee and Brockville, with more than 15 centimetres of snow on the ground in some areas.
One pileup forced the Ontario Provincial Police to close a section of Highway 401 eastbound from Odessa, which is 60 kilometres east of Belleville, to near Kingston. Traffic is being diverted around the area.
Vilela said he's seen reports that the crash involves dozens of vehicles, though the OPP would not estimate the number of vehicles involved.
The OPP sent out a Twitter message just after 2 p.m. ET saying the section of Highway 401 eastbound would likely be closed for "several hours."
The OPP was reporting that the poor weather was moving east, creating worsening road conditions in the area of Kingston, Napanee and Cornwall with multiple minor crashes reported.