The 21-year-old driver of a Kittery Recreation Department van that crashed Friday will be placed on leave while the town investigates the circumstances of the crash, the Kittery town manager said Sunday.

Kittery town manager Kendra Amaral said everyone who was injured in the crash also were had been released from area hospitals, including one child who was transported to a Boston hospital with serious but non-life threatening injuries.

“I have launched a full investigation into the circumstances that led to the crash,” Amaral said in a statement posted online. “As a matter of protocol, the driver is being placed on leave while the internal investigation is being conducted.”

John E. Guy, of Kittery, was driving the van when he suffered a medical emergency and drove off the road into a tree, crushing the front end of the 2010 GMC Savana transport van. He and another counselor, 18, were seriously injured in the crash. A child was also transported from Exeter Hospital to Boston Children’s Hospital with life-threatening injuries, but that child has now been released.

The others in the van were taken to hospitals in Exeter or Portsmouth, New Hampshire. With the one exception, the children’s injuries were not serious and all were home with their parents by the end of the day Friday.

The bus was carrying 11 children between the ages of 7 and 9, along with two counselors—one of whom was driving— when the vehicle veered off the highway and struck a large tree along Interstate 95 in Greenland, N.H., according to New Hampshire State Police.

The children were part of a summer program operated by the Kittery Recreation Department, and were on a field trip to the Candia Springs Adventure Park, a water park in Candia, New Hampshire, police there said.

The van was behind two buses that were also taking children from Kittery to the water park. The buses continued on to Candia, their drivers apparently unaware of the crash, police said.

Although Guy is only 21, Maine Secretary of State Matt Dunlap said that driving a passenger van such as the GMC Savana does not require a special license or training. Someone of Guy’s age “has probably had their license at least two years,” Dunlap said. “Driving a van full of kids is certainly not out of the realm of the legal or the possible.”

Maine law restricts new drivers under 18 from driving children, unless they are family members, for the first nine months after receiving a license. Asked about the safety aspects of having a relatively youthful driver drive a 15-passenger van filled with small children, Dunlap said the GMC Savana is “really a family vehicle for all intents and purposes.”

Amaral said she had given consent for police to download the contents the van’s crash computer, which stores and preserves vital information about a vehicle in the seconds leading up to and following a crash.

Depending on what information is stored in the device, it could help police pin down facts such as whether the brakes were applied before the wreck or if parts of the vehicle malfunctioned.

The Kittery summer camp, which runs for a nine-week session, is part of Kittery’s SAFE – Safe Alternatives for Enrichment – program. For a full summer, the camp costs $1,350; the weekly rate is $175. That includes regular outings involving transportation. Upcoming trips include Kingston State Park in New Hampshire and Funtown in Saco.

Amaral said the camp is still planning to conduct planned field trips in the coming weeks, but will exclusively use a contractor for transportation.

Upcoming trips include Kingston State Park in New Hampshire and Funtown in Saco.

The New Hampshire State Police asks anyone with further information or who witnessed the accident to contact Trooper Andrew Wilensky by phone at 603-223-8715 or by email at Andrew.Wilensky@dos.nh.gov.