Story highlights Seattle Mayor Ed Murray calls the blast a "devastating disaster"

The early Wednesday blast in Seattle's Greenwood neighborhood shatters glass two blocks away

All 9 firefighters sent to Harborview Medical Center have been released, the Seattle hospital says

(CNN) A natural gas leak may have caused a massive explosion early Wednesday in Seattle's Greenwood neighborhood -- obliterating at least one building, damaging many others and sending nine firefighters to the hospital.

Seattle Mayor Ed Murray called the blast a "devastating disaster" for the business district.

"It's going to take a lot of work to help these businesses become vibrant and vital again, but we are committed to that as a city," he told reporters.

One battalion chief and eight firefighters were transported to Harborview Medical Center after the incident, said Seattle fire spokeswoman Corey Orvold. These eight men and one woman all had been released as of 8 a.m. (11 a.m. ET), according to the hospital.

"Thank God, no one was seriously injured, and hopefully, at least as far as we can tell, no one was killed here," Murray said Wednesday afternoon.

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