Haas F1 driver Magnussen made a good start from eighth place on the grid in the Spanish Grand Prix, allowing him to go side-by-side with Hamilton as they entered Turn 4 on the opening lap.
Magnussen tried to overtake Hamilton around the outside of the corner, only for the two drivers to touch, sending Magnussen into the gravel. Hamilton was left with damage, causing him to drop to the back of the field.
It would end any hope of Magnussen fighting for points in Spain as he spent the remainder of the race running in the bottom three positions.
Soon after the clash, Magnussen swore over team radio to his engineer and said: "Lewis knew what he was doing there, he rammed me."
The stewards noted the incident, but deemed it was not necessary to take any further action and launch an investigation.
Asked after the race what he meant by that comment against Hamilton, Magnussen said it was "nothing".
"It was just in the heat of the moment," Magnussen explained. "You say whatever you say, and then you go and look at it. And it's often a different story."
Magnussen admitted in the media pen that he was yet to watch back the incident with Hamilton, leaving him unsure of who was at fault for causing the collision.
"You're always pissed off in the heat of the moment, but I'll go and watch it again, see what happens and then move on," Magnussen said.
Hamilton felt he was "on a normal line" through the corner and that Magnussen "came out of nowhere and hit me".
"He came from behind, and then hit the side of my car," Hamilton said. "I can't say anything about it, it is what it is."
The incident contributed to Haas's failure to score in Spain as Mick Schumacher slipped to 14th in the closing stages after being jumped by a number of the three-stopping cars.
Magnussen thought Haas "had a faster car than a lot of cars to score points today" but was encouraged by the fact the team had performed so well despite not bringing any updates to Barcelona.
"The pace of the car has been good this weekend," Magnussen said.
"Despite everyone, most people, bringing upgrades, we were able to stick with them. So there's a lot of positives that we will carry on to Monaco."