NEW DELHI — The streets were packed Wednesday night when the first explosion ripped through the air.

A car powered by compressed natural gas was traveling through a bazaar in Dhaka, Bangladesh’s capital, when the cylinder stored in the back exploded, witnesses said.

The blast flipped the car. It then ignited several other cylinders that were being used at a street-side restaurant. Then a plastics store on the ground floor of a nearby building caught fire. Then a small shop that was illegally storing chemicals burst into flames.

A wall of fire surged across the street, engulfing bicycles, rickshaws, cars, people, everything in its path. The inferno claimed at least 70 lives in one of the most historic neighborhoods in Bangladesh, a country where hundreds have died in recent years in fires that tore through crowded, unsafe structures, and where a promised crackdown on building violations has fallen short.

“So many people were trying to escape,” said Mohammad Rakib, a restaurant manager, who watched a rickshaw driver try to outrace the flames and then get burned alive.

“I was so terrified,” he said, “I ran out of the restaurant and left behind all the money.”

Bangladesh, one of Asia’s poorest countries, is very crowded — it is about the same size as Iowa, but, with 170 million people, has more than 50 times the population. Those conditions, however, tell only part of the story.

“This isn’t about poverty, it’s about greed,” said Nizamuddin Ahmed, an architect in Dhaka. “The people storing these chemicals in residential buildings are rich — they have cars, nice homes, children studying abroad.”

Government officials need to “knock on doors and tell these businesses to get out and get lost,” he said.