Nah, just fill the tunnel from a zippo track.
Most domestic police dept. don’t have tracked APC’s let alone one with a flame thrower .
What they do have/get on short notice are tear gas grenades ,blue/silver tarps & a leaf blower. Cover the tunnel entrance with the tarp weighed down around the edges ,put gas mask , drop gas grenades down the shaft to the tunnel use the leaf blower to blow the gas down the tunnel.
Get on the roof with a set of binoculars & look for were the folks come running out of a building hacking coughing & puking & that is were the other end of the tunnel is .