Five students at Old State Elementary School suffered non-life-threatening injuries Friday morning when their school bus was rear-ended on U.S. Route 13.

Five students at Old State Elementary School suffered non-life-threatening injuries Friday morning when their school bus was rear-ended by an SUV on the shoulder of southbound U.S. Route 13.

Four of the five students were treated and released from Middletown Emergency Room by 1 p.m., while the fifth student was taken to Christiana Hospital and was expected to be held overnight for observation, school officials said.

The driver of the vehicle that rear-ended the bus, 43-year-old Smyrna resident Curtis Morris, was taken to Christiana Hospital, where he was listed in critical condition Friday afternoon

The crash occurred on the shoulder southbound Route 13 about 7:55 a.m. as Bus #90, owned by the Watson Bus Company, was making its first stop of the morning at the Frederick Lodge mobile home community, according to Delaware State Police spokesman Cpl. John Day.

Bus driver Carol Shane, a 43-year-old Townsend resident, had activated the bus' flashing red lights and stop sign and students were still boarding when Morris' southbound 2003 Volvo XC90 struck the bus, Day said.

After the initial collision, the Volvo ran off the road and possibly struck one of the students still waiting to board the bus.

The crash remains under investigation and no charges had been filed as of late Friday afternoon.

Day said it has yet to be determined what caused the Volvo to leave the travel lanes of Route 13, but alcohol does not appear to have been a factor.

Parents of the injured students were notified of the incident immediately after the crash was reported. Parents of all students at Old State Elementary and Spring Meadow Early Childhood Center also were sent notification of the crash via telephone by about 9 a.m., district officials said.

Old State Elementary School Co-Principals Rene Nolan and Don Davis also visited the injured students and their parents at the respective hospitals.

"This is certainly not a phone call you never want to get, regardless of whether you're a parent, a principal or a superintendent," said Superintendent Matthew Burrows, who was attending a conference outside the district Friday. "I think we're all just very thankful none of the students involved suffered any major injuries, and our hearts go out to the family of the man that hit the bus."

Burrows said an initial investigation indicates the bus driver had followed proper procedure and active the bus' flashing lights and stop sign before the crash occurred.

"Student safety is our top priority and we spend a lot of time working on bus safety to make sure our kids are as safe as possible when they're being picked up," he said. "We constantly review our stops and will take a look at this [stop] in light of todays' incident."

The crash disabled the school bus, requiring district officials to request a second bus to complete Bus #90's route, according to Appoquinimink School District transportation supervisor Gregg Tulowitzky.

This is the first bus crash in several years in which Appoquinimink School District students had to be hospitalized, he added.