A spokeswoman for the office of the city’s chief medical examiner, which performed an autopsy on Tuesday, said the office was conducting further studies to determine the cause of death.

By Tuesday, Ms. Strautmanis’s business had been ordered to shut down amid revelations that it had never been licensed — one of many unlicensed city day care centers that operate outside the law and come to regulators’ attention only when a child is hurt.

The city’s health department received a report of illegal child care activity at the Greene Street loft in November, but an inspector who visited the site could not confirm the allegation, Christopher Miller, a spokesman for the department, said on Tuesday. Workers at the business on the ground floor of the cream-colored building denied seeing any signs of a day care operation, and the inspector did not see any activity while watching the door, Mr. Miller said. No one answered the bell. Eventually, the complaint was dropped.

The department is stepping up efforts to track down unlicensed day care operators, Mr. Miller said, including searching online for listings and advertisements. Any provider that is found to be operating illegally is sent a cease-and-desist order, and inspectors follow up to make sure the site is closed.

Parents looking for child care for the first time often do not know that providers are supposed to be regulated, although awareness has grown in recent years, said Nancy Kolben, the executive director of the city-based Center for Children’s Initiatives. Instead, they may choose based on a center’s reputation among friends and other parents. And parents of infants and toddlers, for whom care is less widely available and more expensive than for older children, may be especially likely to choose an unlicensed option, she said.