Updated

Additional bodies will likely be found in the debris of an apartment explosion and fire in Maryland that has already claimed three lives and injured more than 30 people, police said Friday.

Montgomery County Assistant Police Chief Russ Hamill declined to say at a news conference how many people may still be unaccounted for in the explosion, which happened late Wednesday night.

Two bodies were found Thursday, and a third was recovered Friday, police said. Those victims still have not been identified. Hamill said that the condition of the bodies made it impossible to determine their age or sex.

The county's acting fire chief, David Steckel, said that the recovery process has been slow because of how badly the building was damaged.

"The building still presents as a collapse hazard, which is a dangerous situation for the personnel," Steckel said. "The movement of debris itself presents a challenge. Every time you move something, it has the possibility to impinge the integrity of the structure so we have to be careful and methodical."

Steckel said 50 fire and rescue personnel were working on the recovery efforts.

Another factor slowing the investigation, police said, is trying to determine exactly who lived in the complex, and who was there at the time of the explosion. In some cases, more people may have lived in a specific apartment than were listed on the official records.

Hamill said that investigators have accounted for about 110 people residing in the building, and he said they are still asking family and friends to contact them "until we can account for everyone who is in the building."

Erick Jimenez, who spent Thursday looking for his father, Caesar Jimenez, was losing hope Friday as his father continued to be unaccounted for.

"We've called everyone, but we don't have any positive answer," he said.

Witnesses described the explosion like a bomb going off, and people more than a mile away reported their homes shaking.

Debris was scattered over 100 yards, including a door blown across a two-lane road and parking lot, and clothes hanging from a tree like Christmas decorations.

In a 911 call released Friday, when a dispatcher asks the caller the street number of the building on fire, the caller responds, "There's no number on it now. The whole apartment is on fire, from bottom to top. It blew up. Everything's collapsed."

On Friday, authorities were still working to determine the cause of the blast. The Bureau of Alcohol, Tobacco, Firearms and Explosives had roughly 30 people working the investigation, assisting local authorities.

No cause has been identified, but residents reported smelling gas prior to the explosion. Officials responded to calls for a potential gas leak at the complex last month.

Among those injured were three firefighters who were treated and released Thursday. Officials described heroic efforts to save people trapped in the fire.

Montgomery County Fire and Rescue Battalion Chief Dan Ogren said Friday that the bodies from the two confirmed deaths have been taken to the Office of the Chief Medical Examiner for autopsies and identification.

In all, 34 people, including the three firefighters, were taken to hospitals for treatment. Hospital officials said most of those were released later in the day.

Nine hours after the explosion, firefighters on a ladder truck were still using a hose to put out the last of the fire and smoke still was rising from the building.

Firefighters found people on upper floors who needed help, Montgomery County Fire Chief Scott Goldstein said at a briefing. They used ladders to rescue them.

"People were dropping children and jumping out of other windows," Goldstein said. "Everybody was getting out of the building as rapidly as possible."

Initially, fire officials said they were looking for five to seven people who were unaccounted for. Police later said they don't have a firm number.

The Red Cross was working with families to determine their needs.

While Montgomery County is one of the nation's wealthiest communities, the neighborhoods inside the Capital Beltway in this section of Silver Spring are working-class areas, home to large numbers of Central American immigrants.

Paul Carden, regional disaster director for the American Red Cross, said Friday that 60 families will likely need extended assistance.

Roughly 100 people a night have stayed at a Red Cross shelter established at a nearby community center.