A 3-month-old baby died Monday at an unlicensed SoHo day care center — the first day his parents left him there, authorities said.

Little Karl Towndrow of Brooklyn Heights was discovered unresponsive about 15 minutes into his midday nap at SoHo Child Care, cop sources said.

The day care owner, Maryellen Strautmanis, fed Karl around 10:30 a.m, using a bottle of milk his mother left for him, the sources said.

She tried to burp him, but the baby was fussy. Strautmanis put Karl in a bassinet for a nap around 11:45 a.m. — and he went quiet about 10 minutes later, sources said.

The day care center owner checked on him around 12:10p.m. and saw that his lips were blue, sources said. When she couldn’t wake him, she tried to give the baby CPR. But like all the other workers at the day care center, she wasn’t trained in the potentially lifesaving procedure, the sources said.

A 911 dispatcher tried to coach her through it on the phone until first responders arrived, police sources said.

NYPD detectives escort SoHo Child Care operator Maryellen Strautmanis from the 69 Greene St. address where the business is located on Monday.