SAN GABRIEL, Calif. — The building inspectors and police officers walked into the small row of connected town houses here knowing something was amiss. Neighbors had complained about noise and a lot of pregnant women coming and going. And when they went into a kitchen they saw a row of clear bassinets holding several infants, with a woman acting as a nurse hovering over them.

For months, officials say, the house was home to “maternity tourists,” in this case, women from China who had paid tens of thousands of dollars to deliver their babies in the United States, making the infants automatic American citizens. Officials shut down the home, sending the 10 mothers who had been living there with their babies to nearby motels.

“These were not women living in squalor — it was a well taken care of place and clean, but there were a lot of women and babies,” said Clayton Anderson, a city inspector who shut down the house on March 9. “I have never seen anything like this before. We really couldn’t determine the exact number of people living there.”