MIDDLETOWN, Conn. -- Investigators looking into what caused Sunday's fatal explosion at the Kleen Energy power plant in Middletown said Tuesday night that they were getting closer to determining a point of origin.

About eight to nine people remained at the site late Tuesday night and planned to return early Wednesday morning.

Investigators remained at the plant Tuesday night, trying to gather as much evidence as possible before Wednesday's winter storm hits and snow covers the debris and potential evidence. Investigators said they won't rush the process of finding and gathering evidence and said the process must be slow and methodical.

"The snow is definitely putting a kink in this thing," said Middletown Deputy Fire Marshal Al Santostefano.

Even if crews lay down tarps to help protect some of the evidence, the forecasted high winds could still blow slow and an officer must stay at the plant to guard the scene.

In the meantime, crews had hoped to clear the gas line at the Kleen plant, but that's been postponed until Thursday because of a missing part.

Fire officials warned that during the test, nearby residents might hear hissing or smell gas.

"It's just to get the product out of the line, the line that goes into that building," said Santostefano. "For safety reasons, the personnel who are in there, they want that line evacuated so the building will be safe."

Investigators have a 72-hour search warrant for the plant, but with the storm, it could be extended so police can have more time to determine what caused the massive blast.

Investigators said Tuesday that it was premature to discuss a possible cause of the explosion, including suggestions that a welding torch was left on.