It was initially believed that the session was stopped because of Carlos Sainz, who went off the track after a tangle with Oscar Piastri.
However, it was soon revealed that Perez, Magnussen and Nico Hulkenberg were all caught up in an incident at the first corner.
Who was responsible for Monaco smash?
Magnussen attempted an overtake on Perez, resulting in the two colliding with Hulkenberg caught up in the smash from behind, destroying the Red Bull and the barriers.
The stewards reviewed the first-lap incident, but decided that no further investigation was necessary, a relief to Magnussen who is already on 10 penalty points- two away from a race ban.
Speaking to Sky Sports during the red flag the Haas driver blamed Perez for the incident claiming he squeezed him into the wall.
"From my point of view, I had a good part of my front on Perez's rear and when he went to the wall I got pushed to the wall and made contact with him," Magnussen said.
"I trusted he was going to leave space for me since I was there. It's not a corner where you're braking into it, it's a bend on the straight so you have to have a car otherwise you leave the other guy no option.
"From my point of view, I was there and I got squeezed to the wall."