EAST BRUNSWICK -- A school bus with 15 kids on board crashed into the back of an Academy passenger bus Monday on Route 18, causing a 4-year-old to suffer a broken leg, police said.

All 15 kids on the school bus were taken to the hospital as a precaution and to provide parents with a central place to pick them up, said Sgt. Sean Tulane of the East Brunswick Police Department. The only injury was to the 4-year-old with a broken leg, he said.

The Academy bus was stopped in the right lane of Route 18 as passengers got off the bus when it was struck from behind by the school bus, Tulane said. No injuries were reported on the Academy bus, he said.

The school bus was headed to Netivot, an orthodox Yeshiva school on Ryders Lane in East Brunswick. The injured student was seated closest to the bus' door, police said.

No charges have been filed as of 2 p.m.

Bob Barz, an employee at National Estate Jewelers on Route 18, said he arrived at work to emergency vehicles at the intersection.

"I just saw a couple kids being walked into an ambulance," Barz said.

The crash took place near Edgeboro Road and backed up traffic between Edgeboro Road and the entrance to the New Jersey Turnpike, according to 511nj.org, the Department of Transportation's traffic website said.

Though the bus has a New Jersey Transit logo and lettering it is leased to Academy, which hired the driver and operates the route, NJ Transit said.

Editor's Note: This post has been updated to reflect new information from police about the injuries in the crash.

Jeff Goldman may be reached at jeff_goldman@njadvancemedia.com. Follow him on Twitter @JeffSGoldman. Find NJ.com on Facebook.