The scene looked as if buildings were collapsing in a billow of debris as they did on Sept. 11, 2001 when the World Trade Center in lower Manhattan was destroyed.
"We ran down 43 floors thinking we were going to die," she said Megan Fletcher, 35. "It looked like when the buildings collapsed on 9/11," said Fletcher, who works for an Australian company in the Chrysler Building. "It was terrifying."
Police at the scene raised the concern of asbestos being strewn into the air. Rescue workers and those covered in the debris were being decontaminated at the scene by hazardous materials specialists.
Power utility Consolidated Edison said an underground steam pipe had exploded.
Pedestrians sprinted from the scene, many with cell phones glued to their ears, some crying. Some were covered in white ash and soot, others in mud. A small, yellow school bus stood by, badly damaged by the geyser.
Havoc At Rush Hour
"It looked like the World Trade Center had exploded. I saw rocks and pebbles coming down. As I was running I got pelted in the head by rocks and concrete. Steam came up and then the ground started breaking up," said Reggie Evans, an office administrator who was covered in mud.
Authorities evacuated a wide area including the emblematic Chrysler Building.
"This is not a terrorist-related incident. It's a steam explosion," said Deputy New York Police Department Commissioner Paul Browne.
The blast created a havoc at rush hour. Nearly 200 firefighters rushed to the scene, which was crowded with ambulances and fire engines. People wore masks to avoid breathing pollutants.
Kwang Choi, 57, was working at a laundromat one block away when the explosion occurred. "People just kept running. People were saying a building collapsed," he said. "I looked outside -- huge smoke, just like 9/11. I just ran."
Said 50-year-old computer worker Azad Mohamed: "Of course, the first thing you think about is terrorism. It's pretty scary."
Police insisted there was no building collapse. "We have a building that's a bit shaky, but nothing has collapsed," a police spokeswoman said, contradicting early witness reports from the scene that a building had collapsed.