DANVERS - An explosion that leveled houses across a neighborhood spared most of its residents, causing at worst a fractured bone.

Most residents in the area of chemical company CAI were able to walk - or run - from their homes with only minor cuts and bruises. Local hospitals reported 27 people arrived at their emergency rooms to receive care for injuries caused by the early morning blast.

Salem Hospital spokeswoman Jean Graham said seven patients arrived at the hospital shortly after the explosion. Another three would check in by 10 a.m. Graham said most came in with minor injuries and one, who was admitted for observation, suffered a broken bone.

Beverly Hospital saw 14 patients by 10 a.m., spokesman Shawn Middleton said. Nine were treated and then released, three were admitted in good condition, and two were still being evaluated as of yesterday afternoon.

In Peabody, Lahey North had three patients arrive for care around 4 a.m., according to spokeswoman Rose Lewis. The injured were treated for minor cuts and released.

Detective Lt. Martin Foley of the state fire marshal's office said through a spokeswoman that the early hour of the blast probably kept most residents from serious harm.

At 2:45 a.m., most residents were asleep, snuggled under the covers and away from blasted-out windows.

"From his personal observation, it seemed to make sense," said Jennifer Mieth, spokeswoman for the state fire marshal's office.

Had residents been awake and closer to windows, they would have been directly in the line of flying glass, she said.