MALDEN (CBS) – A possible chemical spill at a Malden health care facility sent 17 people to area hospitals Friday.

The employees at the Hallmark Health Center on Savin St. mysteriously became sick, forcing the evacuation of the building.

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“People on the third, fourth and fifth floors having respiratory, nausea,” said Malden Fire Deputy Chief Stephen Almeida.

“The hazmat team did a great job they went in, checked all the floors, they went to the roof,” Almeida said.

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After several hours the building was given the all clear. But the question remains, what caused the employees to get sick?

“It was a small amount of formaldehyde, but so little that it’s hard to say what it really could have been,” Almeida said.

“Certainly, I’d like to know what it was and I guess I’m reassured by the fact that there were lots of people here today that said it was safe to go in, so I did go in and finish my paperwork for the day,” said Dr. Patricia Sereno who works in the building.

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All the patients were released from the hospital Friday night.