Updated: Watertown Police and Fire Responding to HazMat Situation on Arsenal Street

Updated 9:30 p.m. Patch correspondent Stephen Walsh, who is on scene at Arsenal Street, says the medical examiner has arrived as well as someone from the district attorney's office. 

9:15 p.m. The scene on Arsenal Street is still very active as a Waltham Fire hazmat team and a Waltham Fire engine have arrived. 

Patch correspondent Stephen Walsh has said there is a silver car on scene with a note on it saying "poison used, stay away." Walsh also reports there is a body inside the vehicle. 

7:21 p.m. Approximately 12-14 members of the Department of Fire Services (district two) hazmat team are on scene responding to the situation on Arsenal Street. The State Police bomb squad have also responded along with the Reading Fire Department hazmat truck. 

Crews are currently setting up a tarp around the scene as well as a decontamination zone. 

6:57 p.m. The state hazmat team is suiting up on scene and preparing to investigate the incident, which involves a car parked in a lot across from the AutoZone on Arsenal Street.

Watertown Police and Fire say the incident is "very sensitive" at the moment and a detective will give a press briefing shortly. 

6:54 p.m. Watertown Fire have blocked off the scene of the incident, which is located across from 450 Arsenal St. (AutoZone).

Stephen Walsh contributed to this report. 

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Posted earlier:

Police and fire responded to a Tier 3 hazmat situation on Arsenal Street this evening just after 6 p.m., according to scanner reports. 

The staging for the incident is set at , 450 Arsenal St. and scanner reports say multiple buildings have been evacuated. 

Reports from the Twitter feed of firstduephotos (Ted Pendergast) say the incident involves hydrogen sulfide. 

Stay tuned to Watertown Patch for more updates as this incident unfolds.