Firefighters waged a grim search through the shattered and smoldering rubble of two blast-razed East Harlem buildings Thursday, pulling out the charred bodies of four more victims, officials said.

The searchers battled freezing temperatures and harsh winds as they dug. Despite the grim discoveries, they held onto a desperate hope that some of the remaining missing victims may yet be found alive.

“There’s always a chance,” said a law-enforcement source. “People like hope, but its not reality.”

Thursday’s search of the Park Avenue site brought the number of confirmed dead to eight, with four still missing as of early ­evening. The conditions were so brutal, some likened the disaster site to the World Trade Center.

“It’s just like working on Ground Zero again,” said one firefighter. “The smoke in your face, digging through the rubble for bodies. It’s a tough job.”

Another said, “It was an ­inferno. Now it’s a smoldering ­inferno.”

The scene — where 150 city firefighters were working — was still considered an active rescue operation late Thursday. Mayor de Blasio hailed the searchers’ gut-wrenching efforts.

“They’ve been fighting through the wind, they’ve been fighting through the cold — exceedingly difficult circumstances, and they have stuck with it,” de Blasio said. “At various points, the fire got whipped up a little bit again by the wind.”

Investigators were able to answer few questions about the cause of Wednesday’s 9:30 a.m. blast, mainly because the area that needs to be studied is still covered in debris.

“In one word, devastating,” said National Transportation Safety Board board member Robert Sumwalt, referring to his first impression of the scene at East 116th Street and Park Avenue. “You’ve got two five-story buildings that have been reduced to a three-story pile of bricks and twisted metal.”

Sumwalt said probers suspect that a gas leak led to the explosion. They don’t expect to get into the basements of the two leveled apartment buildings until Saturday to confirm their theory.

“Because of the nature of the scene, we are not able to get up close and personal to begin our examination of the [gas] pipe,” Sumwalt said. “We’re not able to do that until the FDNY declares that the area is safe.”

One mystery the investigators want to solve is why the gas line leading into the buildings from a gas main on Park Avenue is still intact. Usually in such cases it is destroyed.

“That’s unlike other pipeline incidents I’ve been to, where the pipe is thrown out of a crater,” Sumwalt said.

When the FDNY clears enough debris, the NTSB said it will conduct a pressure test that should yield some clues as to where the malfunction occurred.

“We have to get to the basement. We have to clean the area out,” said FDNY Commissioner Salvatore Cassano. “We have to dig out the heating units and the meters, places that could possibly be a source of ignition or a source of the leak.

FDNY Chief of Department Edward Kilduff said that approximately 40 to 50 percent of the debris had already been removed and added that probers hoped to have a clear view of the buildings’ inner workings by Saturday.

At a press conference Thursday, Con Edison President John ­McAvoy downplayed claims by residents who said they had complained of gas odors in the area.

He said only two leaks had been reported on the block where the explosion happened, both of which were minor and repaired.

In addition, he said the gas main that supplied the two East Harlem buildings were surveyed last July and that no issues were found.