Anyone know what was happening on the 401 near London today?

Today around 11 I was driving WB on the 401 near Putnam Rd when I noticed a huge convoy of police cruisers from all over southern Ontario (Ptbo, OPP, MTO, Woodstock cruisers… all with lights flashing) escorting empty CN tractors and a whole bunch of other tractor-trailers. Anyone know what was going on?