Speaking exclusively to Football Insider, the ex-Fifa and Premier League referee suggested the authorities will investigate as the game was broadcast live on television.
Celtic fans threw tennis balls onto the pitch less than a minute into the game and it was delayed by three minutes as they were cleared up.
🗣 "There will be a delay because of this nonsense"
— Sky Sports Scotland (@ScotlandSky) November 7, 2021
Dundee's match against Celtic has been halted by fans launching tennis balls onto the pitch.
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The Glasgow Times reported it was aimed at the rumoured appointment of Bernard Higgins in a security and safety role at Parkhead.
A banner read: ‘Fans or Higgins? The ball’s in your court.’
“The referee has done the right thing,” Hackett told Football Insider correspondent Connor Whitley.
“There’s always a danger when objects are thrown, that it masks the opportunity for some idiot to throw something more dangerous than a tennis ball.
“Nonetheless, tennis balls coming onto the football field, a little bit like balloons, you’ve got to get rid of them before the game.
“I remember a Premier League game some years ago. at Bramhall Lane, where Alan Wiley was the referee and he allowed balloons to stay on the pitch. There was a shot on the goal that hit the balloon and the goalkeeper tried to save the balloon.
“That caused a lot of conversation and [as head of the PGMOL] I had to make a couple of visits to Bramhall Lane.
“I do believe, here, the referee handled it sensibly and no doubt was advised by security.
“He’ll put it in his report and the authorities will, no doubt, likely take action. Where a kick-off is delayed, there’s always a difficulty when it’s being transmitted on television. There are timing issues which are important.”