Kevin Hart & The Rock -- Smoke on Movie Set Sparks 'Beef' with Fire Chief (VIDEO)

Kevin Hart and The Rock engaged in some on-set hijinks when shooting for their new movie was interrupted by a minor fire emergency -- which accidentally led to K-Hart kinda pissing off a fire chief.

The Somerville Fire Department tells TMZ they responded to the call early Thursday morning. It wasn't much -- just a light fixture with smoke coming out of it, which took less than 15 mins to put down.

Kevin posted a funny vid with The Rock as they waited for firefighters to do their thing, but in his caption he mistakenly thanked the city of Boston instead of Somerville. The Somerville Fire Chief did NOT think that was a wickid pissa -- he quickly corrected Kev's mistake when we spoke to him.