Student, teacher critically injured after bus overturns in Maryland

A student and a teacher are critically injured after a charter bus carrying 26 eighth-graders overturned on Interstate 95 north of Baltimore, Maryland, this morning, causing massive traffic delays.

The local fire department, Susquehanna Hose Co., said the one adult and one child were taken via helicopter to hospitals after the accident on the southbound side of I-95 at Exit 89.

Everyone else on board -- 25 children from Charles W. Henry School, a teacher, a parent chaperone and a driver -- were taken via ambulances to hospitals, officials said.

Maryland State Police said the cause of the crash isn't known but that "a passenger car was apparently involved in some way" and the driver is being interviewed.

The accident closed both sides of the interstate but both lanes have since reopened.

According to local fire officials, the children and chaperones were heading fromPhiladelphia to Washington, D.C., for today's law enforcement officers' memorial service. Police cadets who were on another bus on I-95 helped first responders get patients off the busand get help, according to fire officials.

This story is developing. Please check back for more updates.

ABC News' Jeffrey Cook contributed to this report.