Two Manhattan Con Edison workers faced a nightmare on the job Saturday when a manhole they were working on suddenly exploded, officials said.

The contractors were inside the hole at Second Avenue and East 110th Street in East Harlem at about 2:20 p.m. when the blast occurred, according to a spokesman for the utility company.

“I heard a large BOOM and then the lights inside the store started flickering,” said witness Janet Adams, who works at a nearby store. “I got scared and was getting ready to run out here.”

Adams watched as other contractors struggled to free one of their colleagues from the manhole.

“They remained calm but you can see in their face they were nervous,” she said. “They finally brought him out and he was out of it, shaking like he was dizzy. They sat him down until the firefighters came.”

Both workers were taken to Harlem Hospital with flash burns to their face, the spokesman said.

The spokesman did not immediately know the cause of the explosion.