President Bill Clinton, who has an office in Harlem, visited the scene, the Wall Street Journal reported, and talked to rescue workers.
Robert Sumwalt, a member of the National Transportation Safety Board, said at a news conference that investigators had been unable to get into the basement area because of standing water.
While the explosion is believed to have been the result of a gas leak, no official determination has been made.
Conditions at the scene were difficult.
"It's just like working on Ground Zero again," a firefighter told the New York Post. "The smoke in your face, digging through the rubble for bodies. It's a tough job."
The eighth body was found Thursday evening, more than a day after the massive explosion. Officials said most of the dead lived in the two five-story buildings, which had apartments, a church and a piano store.
At least 60 people were injured.
A Con Edison spokesman said someone called Wednesday morning shortly after 9 a.m. to report a gas leak. The utility dispatched a truck immediately, but by the time it arrived the buildings had been leveled.