The workers started their search for a gas leak three rowhouses away, he said. When they arrived at the home where the explosion was about to occur, they could not get inside because no one answered the door, O'Sullivan said.
The PGW workers called a locksmith, which is standard procedure when they cannot enter a home to check for a gas leak. Before the locksmith arrived, someone let them in. O'Sullivan said it was unclear whether that individual lived in the home. The PGW workers entered around 7, he said - just minutes before the explosion.
Once inside, they discovered a "significant" atmospheric reading of natural gas, O'Sullivan said. They called the Fire Department around 7:05 and Peco a minute later to shut off electricity, O'Sullivan said.
Fire Commissioner Lloyd Ayers said the first call about a fire on the block came at 7:04 - followed a minute later by calls from residents reporting an explosion.
The blast shook the street. A fire erupted in the rowhouse with the high natural gas readings.
Nancy Balderas, who lives four doors away, said she saw a cloud of smoke and heard people screaming, "Get out of the house!"
She threw her husband's brown coat over her wailing 20-month-old daughter, Melissa, and tried to run outside, but she said rescue personnel told her to stay indoors. Balderas stuffed her door and window creases with wet towels as smoke poured in.
"It was very, very scary," said Balderas, 36.
O'Sullivan said PGW officials would have evacuated the area if they had obtained high readings of natural gas on the street.
There was no history of gas-main leaks in the area, he said.
Two PGW workers were burned in the incident, O'Sullivan said. Both were hospitalized with non-life-threatening injuries. Their conditions were unavailable late Friday.
More than a dozen people were displaced by the explosion. Most remained in a Red Cross shelter Friday night.
Three officials with the Pennsylvania Public Utility Commission took notes Friday at the scene. The PUC typically investigates the response to such episodes. PUC spokeswoman Jennifer Kocher said the commission was in the "infancy" of its investigation.
The commission fined PGW $400,000 last year for a gas explosion in 2011 in Torresdale that killed a 19-year-old PGW worker and hurt five others. PGW was also ordered to improve its responses, such as the recommendation to shut off electricity in emergency situations.
Crews on Friday boarded up the charred two-story rowhouse. The adjacent home of Xuan Nguyen, 53, was damaged, after she said fire crews broke a window and tore a hole in the roof to spray water inside.
Inquirer staff writer Andrew Maykuth contributed to this article.