LAWRENCE — An 18-month-old girl fell 40 feet from a second-story apartment house window and was in critical condition last night with a fractured skull.

"She was lying on her back. She looked like a rag doll," said neighbor Don Nadeau, who said he heard the child hit the ground.

Police said the child, identified as Franciny Paulino, apparently pushed through the screen of a window at the back of the apartment at 64 Manchester St., and then fell through while her mother was sitting on the porch at the front of the apartment about 7:20 p.m.

Police identified the mother as Josefina Martinez, 49.

The child was first taken to Lawrence General Hospital, but was transferred by ambulance to Massachusetts General Hospital in Boston, where she was in critical condition last night with a fractured skull and internal injuries, police said.

Police Chief John Romero said the toddler couldn't be taken by helicopter because of thunderstorms.

Nadeau said he looked up when he heard the girl hit the ground. He was in the yard of his house on Blakelin Street, which is across the street from the window where the girl fell.

"I heard a thump," he said. "I won't forget that noise for the rest of my life."

He said he immediately went over to the toddler and called out to others who were gathering to call 911.

He said he checked her pulse and gave a few puffs of air into her mouth. He said she did start breathing and he could feel a pulse. He said he stayed with the girl until paramedics arrived.

Yolanda Rosa, a resident of the same three-story brick apartment building, was on the first floor of the apartment when she heard the falling screen from the window hit her door and then heard the toddler hit the ground.

She said she ran out to the toddler and saw that she had blue lips and wasn't moving. A large crowd was already gathering and Rosa said a woman had kneeled next to the girl to pray.

Then Rosa heard the toddler's mother.

"The mom was running and screaming, 'My daughter, my daughter,'" Rosa said.

Rosa said she and another neighbor stayed with Martinez until the paramedics arrived.

"She was too distraught to even look at her daughter," Rosa said. "We had her at the other side of the building."

Romero said it appears like the fall was an accident, but the investigation is still open. The crime prevention and control unit for the Essex County district attorney's office was called in and the Department of Social Services was notified.

Such accidents have occurred with some frequency in the Merrimack Valley over the past several years.

In August 2005, a 2-year-old boy survived an 18-foot fall from a second-story window to a concrete sidewalk on Boston Street in Lawrence.

In July 2006, two bags of bark mulch broke the 23-foot fall of a 14-month-old boy who tumbled out of a third-story window at 41 Cedar St. in Haverhill.

In October 2006, a 2-year-old girl tumbled out of a second-story on Dattilo Road in Derry, N.H., landing head first on a cement driveway 14 feet below, but survived.

In September 2007, a 7-year-old boy suffered serious leg and internal injuries after falling from a third-floor window of a house at 10 Graichen Court in Lawrence.