NEW YORK (CBSNewYork) — Residents in an East Side neighborhood were shaken out of sleep early Sunday morning by bellowing explosions.

“I thought I heard maybe two or three booms, and that was it. So I was curious and came out and saw all the police cars,” one person told CBS2’s Hazel Sanchez.

“And the last few days there has been so much ice falling off the building and that alone sounds like an explosion, but this was so much louder even than that. I knew there was something up,” Kevin Lynch added.

At around 4:30 a.m. the FDNY responded to reports of fire and smoke coming out of multiple manholes on East 56th Street between First and Second avenues. Fire crews stayed on scene for more than three hours, convinced the situation was under control. But then at around 7:40 a.m. there was a massive explosion that was so powerful, it blasted through the street.

Two cars were damaged.

“We had three injuries. One to an EMS operation personnel from the explosion, one from a Con Ed personnel from the explosion, and one firefighter injured with difficulty breathing throughout, during the operation,” Deputy Asst. Chief John Sarrocco said.

More than 200 firefighters responded to the two-alarm emergency and there were extensive searches done at all the surrounding buildings. Carbon monoxide levels were through the roof. There were multiple power outages, firefighters had to search elevators and the apartments of people who need the electricity for life-support systems.

“You worry about the infrastructure, you know. The infrastructure is too old for the number of people using it, you know? It’s kind of scary to be honest, but the response is amazing and I hope everybody is safe,” Lynch said.

Con Ed crews expected to be at the scene for most of the night as they try to restore service to around 500 customers. The utility said it hopes to have everyone up and running by 7:30 a.m. on Monday.