ALLENTOWN, Pa. -

Five people were killed in a powerful explosion that sparked an inferno in Allentown late Wednesday night, said Lehigh County coroner Scott Grim.

Authorities said the five victims who were found in the rubble were a four-month-old boy, a 16-year-old girl, a 69-year-old woman, and a 79-year-old man. The gender and identity of the fifth victim will need to be determined through DNA testing, the coroner said. Officials are not yet releasing the names of any of the victims.

A cadaver dog from the Poconos had been brought in to help with the search for the final victim.

"Our heart goes out to the families that were affected by this tragedy," said Allentown Mayor Ed Pawlowski during a news conference seen live here on WFMZ.com on Thursday.

The massive fire, which followed the explosion at North 13th and West Allen streets around 10:50 Wednesday night, destroyed a row of eight homes, damaged more than 30 other homes and 10 businesses, and forced hundreds of people to flee their homes.

Pawlowski initially told 69 News that the blast, which rocked the city and many surrounding suburbs, was sparked by a leak of natural gas. Dan Adamo, a spokesman for Reading-based UGI, however, said he was unable to confirm that.

UGI crews worked for several hours, breaking through a layer of ice and the surface of the street, to stop the leaking of gas, which fueled the intense fire. Firefighters were then able to get control of the fire and allow evacuated residents to return to their homes shortly before 4:20 a.m.

Allentown Fire Chief Robert Scheirer said two homes in the 500 block of North 13th Street were leveled by the explosion; six others were destroyed by the gas-fueled fire that followed the blast. At least 16 others were damaged.

"When fire crews arrived on the scene the buildings were too damaged to actually put firefighters inside the building to fight the fire, so we had to do a defensive tactic and basically fight it from the outside," said Scheirer. "So it really takes a long time to put a fire out fighting a fire in that mode."

Pawlowski said the neighborhood would be rebuilt and that he is working with federal officials, including Pa. Sen. Bob Casey, to help the displaced residents.

"My office of constituent services is available to assist Allentown families with any issues to ensure that they continue to receive the support they need," said Casey in a written statement released by his office Thursday afternoon. "While a full investigation is ongoing, incidents such as these highlight the need to update our aging infrastructure. My thoughts and prayers are with the families affected by this tragedy.?

69 News viewers called or emailed from Allentown's northern suburbs, Bethlehem, and as far away as Center Valley and Breinigsville, Pa. to report that their homes shook from the explosion.

Skiers at the Bear Creek Ski Resort in Longswamp Township, Berks County reported seeing the large plume of smoke from atop the mountain.

Initial reports from the scene indicated multiple people were injured, but officials said the intense fire initially prevented them from being able to confirm any injuries or fatalities.

Lehigh Valley Hospital in Salisbury Township said it was set up to treat multiple victims, but did not received any patients.

A woman who lived in the 500 block of North 13th Street told 69 News she was in bed with her husband when the explosion happened. She said part of the ceiling collapsed on them. They managed to escape their home with only minor injuries, wearing not much more than the clothes they had on for bed.

A firefighter was injured when he slipped and fell on a patch of ice.

Some 700 residents who live near the scene of the explosion were evacuated from their homes. Many of the evacuees, including residents of the Gross Towers apartment building, were loaded onto LANTA buses and taken to Ag Hall at the nearby Allentown Fairgrounds, where the Allentown Bureau Of Health and the American Red Cross set up a shelter with cots, food, and water.

The Comfort Suites In Dorneyville offered free rooms Wednesday night for people displaced by the explosion and fire. People who needed transportation to the hotel could call 610-437-9100. The hotel was unable to accommodate pets.

Debris from the explosion was thrown far and wide, reportedly being found several blocks away.

Police closed many neighboring streets around the area as dozens of firefighters from across Allentown and around Lehigh County rushed to battle the massive fire, which was fueled for several hours by the leaking gas. Crews from Emmaus and Cetronia were among those on the scene.

The freezing weather hampered the efforts of firefighters. Ice from the water they used to fight the flames formed on power lines and covered streets and sidewalks.

About 100 PPL customers in the area lost electricity as a result of the explosion. PPL said those customers will remain without power until the fire department says it's okay for PPL to restore it.

The Allentown School District closed Luis Ramos Elementary School and the IBEAM Academy, which are near the scene, on Thursday. Staff was asked to report at 10:00 a.m.