In a statement the Northern Ireland Ambulance Service said they received a 999 call at 07:42am following reports of a collision in the Magherafelt Road area, Castledawson this morning.
"NIAS despatched 4 Emergency Crews, a Doctor, an Officer to the scene and also tasked the Charity Air Ambulance, with HEMS crew on board, to the incident.
"Following assessment and initial treatment one child was taken to the Royal Belfast Hospital for Sick Children in Belfast by ambulance while another patient was taken to the Royal Victoria Hospital, also by ambulance.
"Two other patients were taken to Antrim Area Hospital by ambulance," said the statement..
The NIFRS confirmed that one person was rescued from their vehicle by firefighters using cutting equipment
According to TrafficwatchNI there is no access to the A31 Magherafelt By Pass & Castledawson Road from Castledawson Roundabout.
A Tweet on the site adds that "the County Londonderry road at the Castledawson Roundabout remains partially closed following a serious RTC earlier this AM".
It adds that "@NIRoadPolicing collision investigators examining the scene".