Referee Trevor Jones’ blast of the whistle for full-time was the cue for the start of a brawl involving many of the players and some of the coaching staff.
Police officers visited both dressing rooms after the 1-1 draw – a game which the Lilywhites led deep into stoppage-time.
Things had been bubbling under in the closing stages of the game.
North End striker Jason Harris had been sent-off for two bookings to raise the temperature.
Then, when Northampton didn’t give the ball back after PNE keeper Tepi Moilanen had kicked it out of play to get treatment for an injury, the tension really rose.
The Cobblers equalising right at the death just sent things over the edge.
North End had gone into the game top of the Second Division table.
They started well and took a sixth-minute lead.
Paul McKenna sent over a free-kick from the left, which Town defender Colin Hill managed to head into his own net.
David Eyres was close to a second with an overhead kick which flashed just past the post.
Cobblers keeper Andy Woodman twice denied Kurt Nogan, the striker also just too high with a header.
Then Harris managed to get a touch on a cross from Mark Rankine but couldn’t direct it into the net.
Conditions were difficult, the pitch soaked by heavy rain.
The wind swirled around the ground and until the last few minutes of the first half, North End clearly coped the better with it.
Northampton began to work their way into the game, Moilanen forced into a fine save from Carlo Corazzin.
Moilanen went on to make a string of saves in the second half as the home side got well on top.
That said, Nogan missed a golden chance to put the game to bed in the 77th minute.
He hit the post with a shot after keeper Woodman had miscued a goalkick straight into his path.
It was moments after that chance that tensions started to rise.
Moilanen threw the ball out of play so that the physio could come on to attend to his leg injury.
Alistair Gibb didn’t give the ball back from the throw in, choosing to pick-out a team-mate.
That led to a corner which North End managed to clear, Harris chasing after the ball and fouling Hill.
It happened in front of the dug outs, the Cobblers bench going up to loudly appeal.
That earned Harris his second yellow card of the game and off he went for an early bath.
Preston’s 10 men held out until the 95th minute when James Hunt headed home from Sean Parris’ cross.
Then came the Battle of Sixfields, the teams wading into each other with at least two people going to the floor in the chaos.
PNE: Moilanen, Parkinson, Jackson, Kidd, Ludden, McKenna, Gregan, Rankine, Eyres, Nogan (Appleton 84), Harris. Subs (not used): Cartwright, Murdock.