Update 5:30 p.m.: Lower Merion Fire Chief Chas McGarvey said the chemical is a type of acid—either sulfuric or muriatic—and that the reason there was a cloud may have been because there was moisture on the ground. Another fire official said there is no cause for concern. Officials are currently neutralizing the spill and the scene should be clear by about 6 p.m.
Update 3:38 p.m.: Lower Merion Fire Chief Chas McGarvey said a witness reported a liquid chemical was thrown out the window of a vehicle. The vehicle did not stop, and it is unclear whether there was an intended target for the chemical, he said. A description of the vehicle is not yet available.
Lancaster Avenue in Ardmore has been closed between Greenfield Avenue and Haverford College since about 2 p.m., when police said a foot-long canister fell off a truck and discharged an unknown substance.
Police are detouring traffic at either end of the closure, and authorities issued a bulletin at 2:45 p.m. telling motorists to avoid the area for the next hour "due to a HAZMAT situation."
HAZMAT crews arrived on scene just after 3 p.m.
Firefighters with gas masks are also on the scene. A witness told Patch he saw the object let out a big cloud of white smoke.
One officer said the canister "let out a chemical, let out smoke, we're not sure what it is ... some sort of gas."
A firefighter told Patch at 2:45 p.m. that township authorities were expecting a county hazardous-materials crew to help at the scene this afternoon.
Keep checking Patch for updates on this story as authorities work.