28 Kids and Staff Members Hospitalized After Carbon Monoxide Leak at Pennsylvania Day Care Center

Over two dozen people were taken to local hospitals by ambulance after high levels of carbon monoxide were detected at a Pennsylvania day care center on Tuesday, officials say.

The Allentown Fire Department "responded to a medical call" at Happy Smiles Learning Center on Tuesday morning, the city wrote in a statement.

"When AFD arrived on the scene to treat the unconscious child, a carbon monoxide (CO) monitor on the firefighter's equipment started beeping and alerted the team to an issue," read the city's statement.

Afterwards, the firefighter went to the meter, which indicated there were "dangerously high levels of carbon monoxide in the building."

Zach DeWever/WFMZ-TV via AP Emergency responders on the scene of a carbon monoxide leak at the Pennsylvania day care center

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25 children and 8 staff members "were immediately evacuated" from the building, the city wrote.

"EMS was on the scene and set up treatment and triage in the parking lot of the facility," they added. "A total of 28 patients were transported by ambulance to four area hospitals to be monitored."

Allentown Fire Department spokesperson Capt. John Christopher confirmed to PEOPLE that 28 individuals were transported by ambulance to local hospitals, but noted that some parents picked their kids up to transport them themselves.

Everybody they took to the hospital was in stable condition, Christopher said.

Daniel Patrick Sheehan/The Morning Call via AP Happy Smiles Learning Center

According to Christopher, one child was found unconscious at the center and there were "people showing multiple levels of exposure."

The day care center did not have a working carbon monoxide detector in the building, Christopher confirmed. He went on to note that local legislation was passed last month that will require all childcare centers to have carbon monoxide detectors, but that the legislation doesn't go into effect until later this month.

The Happy Smiles Learning Center did not immediately respond to PEOPLE's request for comment.

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Zach DeWever/WFMZ-TV via AP Emergency responders arrive at day care center following carbon monoxide leak

UGI Utilities, a natural gas and electric utility company, was called to investigate, a spokesperson tells PEOPLE.

"We determined that CO was being produced by a malfunctioning heating unit and a blocked venting system," the spokesperson said.

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Officials in Pennsylvania are urging everyone to take carbon monoxide safety seriously.

"Every winter the Allentown Fire Department responds to an increase in number of carbon monoxide calls. Gas- and oil-burning furnaces produce CO and can become a silent killer," the city wrote at the end of their statement. "CO is an invisible, odorless, poison gas that kills hundreds every year and makes thousands more sick."

"Those who have oil and gas furnaces should have their furnaces inspected every year," they added. "CO detectors should be checked regularly to make sure they are functioning properly."