Monfries is one of several players who complained of a laser being shone in their eyes on Saturday night during Essendon's four-point defeat.
"There was a laser beam out there. I noticed it a couple of times," Monfries told the Seven Network's AFL Game Day program.
"I was on the mark when Sydney were kicking out once and it was shining around my eyes. It was a bit distracting at the time."
An AFL spokesman confirmed on Sunday several Essendon players complained about the laser to the umpires, who alerted Etihad Stadium security staff.
But they were unable to find the culprit.
The spokesman said there was nothing more the league could do unless someone reported the person using the laser beam.
Handheld laser pointers are not illegal but they are a prohibited item at all AFL venues, and those found to be using them can be evicted from the ground.
The issue also arose in a 2007 match between Richmond and Collingwood at the MCG, where then-Tigers' captain Kane Johnson and Magpie Ryan Cook had a laser shone in their faces.
The problem of players being targeted with lasers has been a problem in overseas soccer matches, particularly for goalkeepers.
Socceroos 'keeper Mark Schwarzer complained of a laser being shone in his eyes during Australia's World Cup qualifier against Oman in Muscat on Friday night.
Schwarzer reported the laser incident to FIFA match commissioner Sunil Senaweera, saying it was a regular occurrence when the team played in the region.
"Every time we come here, the same thing happens," Schwarzer said.
"So I told the referee before the game that I was sure it was going to happen.
"He got it in his face as well."