Emergency personnel respond to Building Blocks Learning Center on Route 236 in Kittery for reports of potential carbon monoxide poisoning on Wednesday evening. Derek Davis/Portland Press Herald

Eleven people who were at a Kittery day care Wednesday were treated and released from Portsmouth Regional Hospital for potential carbon monoxide poisoning, town officials and a hospital spokesperson said.

Seven patients were transported by EMS and four went to the hospital independently, Ellen Miller, a spokesperson for the New Hampshire hospital, said Wednesday night. She described their condition as “fair,” meaning their vital signs were stable.

All of the patients were released Wednesday night, Miller said.

There were 27 children and 10 staff inside Building Blocks Learning Center on Route 236 when police received a call around 3:19 p.m. Wednesday. All Kittery police and fire units and other first responders in the area responded.

Kittery Town Manager Kendra Amaral said the seven people transported by EMS were exhibiting signs of illness consistent with carbon monoxide poisoning. She said the children and staff were accounted for and reunited with family.

The Office of State Fire Marshal is investigating to determine the cause of the potential leak, Amaral said. The fire marshal’s office sent a crew of investigators and inspectors, Department of Public Safety spokesperson Shannon Moss said.

Asked whether an alarm went off at the facility and how authorities learned about the leak, Moss said, “That’s part of the investigation.”

The scene had mostly cleared by 5:30 p.m., with just one Kittery ladder truck and a department pickup truck parked outside the facility. A handful of firefighters could be seen walking inside the building.

Staff Writers Riley Board and Daniel Kool contributed to this report.