Hundreds of firefighters filled Montreal’s city hall Monday in a raucous protest against pension plan changes.

The union workers gathered outside the building in the afternoon, sirens blaring in the background as they set fire to papers, filling the air with smoke.

The crowd, many hoisting placards above their heads, entered the council chambers just before 7 p.m. local time. Councillors exited the room for a short while until demonstrators left, returning to paper debris and stickers across the floor and chairs of the room.

Workers have been protesting since Bill 3, a plan to reform the pension of Quebec municipal employees, was tabled in June.

Parliamentary hearings on the bill begin Aug. 20.

With files from CTV Montreal

Fire fighters protest outside montreal city hall, burn paper @CTVMontreal pic.twitter.com/mwZntsgOBL — Natalie Nanowski (@Natalie_SKi) August 18, 2014

Hundreds of fire fighters protest outside #mtl #cityhall. Fire set outside pic.twitter.com/RAm2hOcGpf — Natalie Nanowski (@Natalie_SKi) August 18, 2014

100s of fire fighters inside cabinet. Councillors gone, possible left in hurry, briefcases on chairs. @CTVMontreal pic.twitter.com/TWbrMqS2U6 — Natalie Nanowski (@Natalie_SKi) August 18, 2014

Councillors cleanup cabinet, firefighters enter again. Meeting was about to restart, protest started @CTVMontreal pic.twitter.com/Avbk3u1fl3 — Natalie Nanowski (@Natalie_SKi) August 18, 2014