I think you're right...Press conference at St. Vincent's in 15 minutes on Fox News. New lady witness, heard a very loud explosion, a couple of doors down, a lot of smoke and debris, "awful smell" -- explosion was at the sign factory, streets blocked off, barricades, etc. Fire official Mike Carter says there was an explosion, civilian injuries only, concern because of recent terror warnings, appears that it smells like hydrocarbon aroma, appears to be a tragic accident...
Howard Safer, former fire commissioner, says it's all speculation "until we see what's in there."
Fox: Police officer at the scene thinks it was boiler explosion...not a gaping hole inside the building, damage may be structural, but no pancake type collapse
Another brilliant eyewitness
"It was a giant boom — a real giant boom," said neighborhood resident Bill Beek, who lives a half-block away. "It sounded like an airplane crashing." Wonder how many plane crashes Mr. Beek has heard in his life???