In a preliminary report on the East Harlem gas explosion and subsequent building collapse on March 12, the National Transportation Safety Board cited “small gas leaks below the pavement,” in a main measuring eight inches in diameter.

The NTSB said that multiple holes had been found in the piping, and escaping gas had saturated the soil around the collapsed buildings for some time before the explosion.

The release of the preliminary two-page report concludes the NTSB’s New York investigation. “The investigation now pivots to Washington, D.C.,” the NTSB said in a statement, “as investigators test sections of pipe secured from the scene and conduct other investigative activities such as examining leak surveys and maintenance records for the gas main on Park Avenue.”

Materials from the site will now be sent to Washington D.C. to be examined. Among those materials are sections of an iron gas main that are more than a century old, as well as pieces of plastic main installed in 2011 and segment of a cracked water main.