An explosion and two-alarm fire in Gaithersburg, Maryland, demolished a portion of two residential buildings Wednesday and sent at least 10 people to hospitals, including four children. Two adults have traumatic injuries, an official said.

The blast tore through the Potomac Oaks Condominium in the 800 block of Quince Orchard Boulevard near Rabbit Road at about 8:40 a.m. Wednesday, officials said. Montgomery County Fire & Rescue received multiple calls reporting the explosion and fire, which sent smoke into the air that was visible from miles away.

“It felt like we were bombed,” said a man who felt the blast from his office nearby. “…My heart goes out to everyone.”

The fire went to a second alarm within minutes. While much of the blaze was extinguished in about 40 minutes, crews were still fighting a gas-fed fire in the basement hours later and continued to battle hot spots that were flaring up.

Video and images from the scene showed a massive wall of orange flames and a gaping hole after the blast leveled a portion of a garden-style apartment building. Smoke choked the gap between two jagged edges of the building that apparently was the site of the blast.

A 50-to-75-foot field of debris and rubble covered the grass outside the building. Large chunks of bricks and cinderblocks were visible.

“Woke up to an explosion out front,” said a man who discovered that a steel door had been blown into his living room.

The force of the explosion was so powerful that two people in the area told News4 their bodies were physically shaken by the blast.

Ten people were taken to hospitals, authorities said. Two adults were seriously injured and were rushed to a trauma center, Montgomery County Fire Chief Scott Goldstein said. Eight other people — four children and four adults — had non-life-threatening injuries, Goldstein said.

Other people were evaluated, Fire & Rescue spokesperson Pete Piringer said, but the situation was still fluid.

There was no information available yet on whether anyone else was unaccounted for. Fire & Rescue crews were working with Washington Gas to shut off the gas, but it was not currently safe to search for anyone else inside the building, Goldstein said about 10:40 a.m.

Maintenance workers rescued two people from an apartment using ladders before firefighters arrived, Goldstein said.

The cause of the fire and explosion is yet to be determined, but Goldstein said there was what appeared to be a “gas-fed” fire in the basement.

After first responders arrived, some residents told them they had smelled gas earlier in the morning.

“The smell of gas this morning had been reported to our investigators,” Goldstein said, but he said 911 staff had not received a call before the explosion about the odor of gas. However, it was not yet known whether anyone might have contacted Washington Gas, any other agencies or building management.

Anyone who smells gas at any time should immediately call 911, Goldstein said.

In a statement late Wednesday morning, Washington Gas officials said they were “aware of the incident this morning in Montgomery County, Maryland. Our personnel are responding to assist the fire department on the scene. As always, the safety of our customers and community is our top priority. We are supporting the active response to the incident and do not have further details to share at this time.”

It wasn’t immediately known how many people lived in the affected units. Goldstein said the Potomac Oaks complex has four buildings with a total of 24 units. Two of the buildings were badly damaged, and the other two were evacuated.

Potomac Oaks resident Traci DiMartini was at work in the District when friends suddenly started calling her phone Wednesday morning, but it wasn’t until the fire department rang that she learned her home of 19 years was gone.

DiMartini, a federal worker who was giving a presentation at the time of the blast, said fire officials were called to account for residents. Soon after, she said she spoke with her downstairs neighbor, who was able to escape.

“She had just gotten out, and I think she was in shock, too,” DiMartini said.

DiMartini spoke with News4 as she raced home to see if her cat, Rocky, somehow survived the explosion. She wasn’t hopeful. She’s also anxious for answers about what caused the blast.

DiMartini told News4 the neighbor across the hallway from her unit was renovating their condo, though it’s as of yet unclear whether that was connected to the explosion. Another neighbor, who also lost her home but asked News4 to not be identified, also said the unit across from DiMartini was being renovated by new owners.

DiMartini grew emotional as she spoke of raising her daughter, who is away at college, in her longtime Gaithersburg condo.

“It’s the only home she’s ever known,” she said.

This is at least the third apartment building explosion in Montgomery County in recent years. In 2016, a massive natural gas explosion at the Flower Branch apartments in Silver Spring killed seven people. Earlier this year, an explosion at another building in Silver Spring injured 14 people after a worker accidentally cut a gas line.

People who were nearby at the time of Wednesday’s explosion said on Twitter they could see smoke from miles away. A video posted by Channing Work just before 9 a.m. showed dark smoke rising into the area. Sirens were audible in the distance.

Multiple roads were closed in the area, which includes apartments, townhomes and commercial space. The nearby Brown Station Elementary School was not affected, but students will dismissed early Wednesday, at 12:30 p.m.

This is a developing story. Stay with NBC Washington for more.