A crash on Interstate 93 in Andover left a mother and her 4-year-old son in the hospital.
Responders rushed to the scene near River Road around 3 p.m.
Officers say a mother and her young child were stopped in the breakdown lane when a car hit them from behind at a high rate of speed.
According to State Police, the impact of the crash sent the stopped vehicle across the highway, where it ended up in the left lane.
The 4-year-old boy and his mother sustained serious injuries from the collision. The driver and passenger of the other vehicle were also injured.
Police say all four people were transported by ambulance to Lawrence General Hospital. The young boy was later taken by helicopter to a Boston hospital.
Debris from the accident caused a traffic back up in the southbound lane for several miles.