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Emergency crews dug through mounds of rubble early Wednesday for two people believed to be missing after an explosion leveled a large section of a Motel 6 near Seattle.

Authorities in Bremerton, Washington, told NBC News the unaccounted for may be trapped following the Tuesday night explosion after attempts to reach them by phone were unsuccessful. A third person also believed missing was located early Wednesday and had not been in the debris.

A gas leak was reported shortly before 8 p.m. local time (11 p.m. ET). Motel workers and patrons had the chance to evacuate just prior to the blast, which happened at 8:24 p.m., authorities said.

Firefighters who were on scene at the time investigating the gas leak were blown back nearly 20 feet, police said.

A gas company worker was critically injured by the explosion and was flown by air ambulance to a hospital with second- and third-degree burns.

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"The shaking was bad enough that the neighbors thought a tree fell on their house,” said Alice Adams, who lives three blocks away. “Both the sound and force made it almost instantly obvious that it was an explosion and not something smaller like a firework explosion or gunshot."

Local resident Beth Olson told NBC News: “It felt like a massive pressure concussion, like a bomb went off.”

She added: “I was sitting on my floor, as was my upstairs neighbor … and as soon as we felt the concussion, I texted him and he called me, simultaneously. He's in the military so he was immediately concerned about that, of course."

Firefighters are going through the damaged area of the motel now checking to ensure everyone was evacuated pic.twitter.com/Bb3RyTGv3f — Bremerton Police (@BremertonPD) August 19, 2015

“I could definitely feel it in my eardrums initially and when we ran outside, it was dead silent — no birds or anything, and the busy street next to us was empty — until the sirens started," Olson said.

The motel's manager, Tonya Hinds, told NBC affiliate KING5 that she pulled an alarm in the building before the blast.

"I knew pulling it was a split-second decision. I thought this could cause major pandemonium, me pulling this alarm, but my gut told me to and I'm glad I did because it gave us time to get everyone away from the building," she said.

The blaze at the site burned for several hours.

Neighbor shared photos in aftermath of Bremerton motel explosion http://t.co/Z0xNtdKCuY Photos via @Eamyoncanoe pic.twitter.com/lrfRVMCGBt — KING 5 News (@KING5Seattle) August 19, 2015

"The management did a really good job of getting the alarm in right away and getting the evacuation started," Bremerton Police Chief Steve Strachan earlier told The Associated Press. "We're very thankful there weren't more injuries."

Bremerton is a town of about 39,000, and is a one-hour ferry ride across the Puget Sound from Seattle.