The state Department of Environmental Protection is investigating whether the landslide that closed Route 65/Ohio River Boulevard in Kilbuck was triggered by bigger explosive charges used the day prior to the slide at the construction site.

DEP inspectors yesterday were reviewing the blasting records of Penn Development Services of Uniontown, which is doing site construction, and its blasting subcontractor.

They also interviewed residents of Roosevelt Road in Emsworth, a half-mile northeast of the construction site at the old Dixmont State Hospital, who reported hearing unusually loud blasting noise on Sept. 18, the day before the slide started.

"We're investigating the cause but right now we have no information to report," said Betsy Mallison, a DEP spokeswoman. "We're looking at the blasting records. So far we haven't found anything but we're still investigating."

So far, the department has found no violations of the blasting permit it granted in October 2005. The DEP did force changes in how blasting was conducted in April, after a smaller landslide.

Ms. Mallison said the blasting charges used Sept. 18 were not only bigger, they were set in the ground at a different angle.

John Atwood, president of ASC Development, the shopping center developer, said he was unaware that bigger explosive charges were used that day or that the DEP was reviewing blasting records.

Representatives of Penn Development Services could not be reached for comment.

The big landslide began the night of Sept. 19, on land ASC Development Inc. started excavating in March. It impacted a plateau being created for a shopping complex to be anchored by a Wal-Mart Supercenter and an expansive parking lot.

An estimated 250,000 to 300,000 cubic yards of material slid, with 50,000 cubic yards coming to rest on Route 65. The slide was 500 feet wide and covered the road with up to 30 feet of debris. The road will likely be closed until Oct. 7.

Ms. Mallison said the department also is reviewing the project's geologic and engineering records. A persistent criticism of the project has been that the slope to the development plateau was too steep and the township shouldn't have waived a requirement to "bench" the slopes, creating giant, step-like progressions on the hillsides to reduce the risk of a slide.

Aside from the ongoing investigations, Ms. Mallison said DEP is focusing on a review of an emergency soil and erosion control plan submitted last Friday. The plan must address changing conditions at the site and provide protection for the local waterways.

"The company can't put the emergency plan into operation until it gets the road cleared," she said. "The priority is getting the road clear."

The department has suspended the company's original erosion and sedimentation control permit, issued in 2004. The order, issued last Friday, also forbids the developer from earth-moving at the site, other than that necessary to implement emergency measures to remove the landslide remnants and stabilize the affected area.

Despite reports that yesterday's rain had delayed earth removal from the highway, Mr. Atwood said that after "reorganizing in mid-morning," bulldozers and trucks ran all day moving material from the highway.