KITTERY, Maine (WHDH) – Dozens of people were forced to evacuate a daycare in Kittery Wednesday by a carbon monoxide leak that sent 11, including several young children, to the hospital.

Investigators confirmed they found high levels of carbon monoxide inside the daycare; crews were on scene overnight to figure out how it happened.

“We were seeing over 10 times the amount of acceptable level of carbon monoxide in the building,” said Kittery Fire Chief Craig Alfis.

The Kittery Fire Department was called to Building Blocks daycare on Route 236 shortly before 3:30 Wednesday afternoon.

“When we got on scene we found children that were complaining of nausea and headaches,” Alfis said.

Twenty seven children and an estimated 10 staff members were inside the building at the time.

“The ambulance staff that we had on scene started attending to the children and triaging the fire staff made immediate entry into the building with gas meters and air packs,” Alfis said.

Seven children and four adults were taken to Portsmouth Regional Hospital for treatment.

““I think the parents, and appropriately so, were the most concerned,” said Marc Grossman, EMS medical director for the hospital. “The kids, some of the kids felt sick and then they got better with the oxygen. They recovered relatively quickly just within a matter of hours.”

The other children who were inside the daycare were shortly reunited with their families.

The cause of the incident is being investigated by the state fire marshal, who said that while there are a lot of questions that still need to be answered, he commends the quick thinking of fire crews and staff.

“The folks that are daycare providers also in recognizing that there was an issue here safely evacuating the children and notifying the fire department was key,” State Fire Marshal Shawn Esler said.

All patients have been released from the hospital, according to sources.

The fire marshal has not confirmed the cause of the leak but expects to have more answers Thursday.

This is a developing news story; stay with 7NEWS on-air and online for the latest details.

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