Workers remain on the scene of an early-morning house explosion and three-alarm blaze in South Philadelphia that was possibly caused by a gas leak. One woman suffered minor injuries.

The incident occurred about 3 a.m. on Naudain Street near 23rd. Several residents called 9-1-1 to report a gas smell, and responding authorities discovered high carbon monoxide readings and evacuated the block. But as utility workers scrambled to pinpoint the smell's source, something set off an explosion at one home.

The American Red Cross relocated about 30 residents briefly to shelter at the nearby High School for the Creative and Performing Arts on South Broad Street; nine residents remain there as of 2 p.m., according to Red Cross spokesman Dave Schrader.