The Merrimac Fire Department reports that crews are currently on scene responding to a crash on I-495 South in the area just after the Broad Street on-ramp.
The on-ramp is currently closed for motorists, and the area is open to one lane of travel, creating significant traffic.
Crews are expected to remain on scene for an extended period of time. The Merrimac Fire Department asks that motorists avoid the area and seek alternate routes if possible, and to follow any posted detours.