NEW YORK (CBSNewYork) — After a new scare involving Legionella bacteria, an Upper East Side school reopened to faculty Tuesday.

As CBS2’s Janelle Burrell reported, staff who showed up at the campus of the Convent of the Sacred Heart School didn’t show any signs of being concerned and offered little comment.

“You can talk to our headmaster,” one woman said.

MORE: Five Facts About Legionnaires’ Disease

“You can speak to Dr. Ciancaglini or Craig MacPherson,” said another woman.

The elite all-girls Catholic school was shut down to faculty Monday after the bacteria was found in a cooling tower. Prekindergarten through 12th-grade classes are housed in two historic landmark buildings, both former mansions.

Over the weekend, the head of the school emailed a letter to parents and staff saying,”While it was only found in small amounts and is unlikely to have infected anyone, we have closed the mansions this weekend to eradicate the bacteria.”

State and city health officials now mandate routine testing as part of recently passed legislation.

They say it’s common for the bacteria to be found in small concentrations, as it was at the school.

But earlier this summer, Legionnaires’ disease proved deadly, killing a dozen people and making more than 100 others sick after an outbreak in the South Bronx.

Health officials said that, unlike on the Upper East Side, the Legionella bacteria was found in very high concentrations in the Bronx.

At Convent of the Sacred Heart, the administration told parents it had the school’s cooling towers disinfected twice to make sure all traces of Legionella are gone.

But Dawn Boland, who teaches across the street, said it still makes her uneasy.

“I’m a teacher as well, so I hope they’ve done all the right things necessary to make sure everyone’s safe. That’s the concern,” she said.

Under the new guidelines, all buildings in the city with cooling towers must be inspected every 90 days.

The Health Department has given the Convent of the Sacred Heart the all-clear to reopen to students next week.

Legionnaires’ disease — a form of pneumonia especially dangerous for the elderly and for people with underlying health issues — can usually be traced to places favorable to Legionella growth such as cooling towers, hot water tanks, whirlpool spas, hot tubs, humidifiers and condensers in large air conditioning systems. It is spread through contaminated mist and is not contagious.

Symptoms of Legionnaires’ disease include headache, fatigue, loss of appetite, confusion and diarrhea.