State Fire Marshal Stephen Coan said yesterday a team of investigators from the U.S. Chemical Safety Board has been denied access to the explosion site on Water Street because they are not trained to carry out criminal investigations, and law enforcement officials have yet to rule out foul play.

"We are not prepared tonight to call this an accident," Coan said. He said state police investigators, agents from the Bureau of Alcohol, Tobacco and Firearms, and Danvers police and fire officials haven't discovered evidence to suggest "criminal intent" behind the explosion, but more time was needed for the "criminal investigation to take its course."

A spokesman for the Chemical Safety Board called the state's position unprecedented in the board's experience. In other places throughout the country, the Chemical Safety Board's investigation happens at the same time as the criminal investigation, according to Daniel Horowitz, the board's director of congressional, public, and board affairs.

"It's puzzling that Massachusetts has taken this posture," Horowitz said. "There is no (other) jurisdiction in the country that has adopted this posture."

An independent government agency that has been operating since 1998, the Chemical Safety Board investigates industrial chemical accidents and makes recommendations to prevent their recurrence. It has investigated 40 accidents since its creation. The Federal Clean Air Act mandates the board be given access to sites such as the one in Danvers, Horowitz said.

A team of Chemical Safety Board investigators arrived in town from Washington, D.C., on Friday afternoon. They haven't left town, despite being denied access. The team will try again today to get on the explosion site, Horowitz said.

"The public interest has to come first," Horowitz said. "Federal law has to be enforced."

Ideally, Chemical Safety Board investigators need access to a site "right away" before evidence is damaged, Horowitz said.

"A lot of what we're looking for is very fragile," he said. "We're looking for blast markers, small bits of damage to structures and beams that in the hands of experts with a computer can pinpoint exactly what kind of explosion this was, perhaps even what kind of materials are involved."

Horowitz said the board has the resources, chemical and mechanical engineers as well as blast experts, to thoroughly respond to situations such as the Danvers' explosion. "This is precisely what we do," Horowitz said.

But the state fire marshal said the criminal investigators must have the "exclusive authority" to work "uninterrupted by other entities."

"We have full recognition and appreciation for the work of the federal Chemical Safety Board," Coan said. But he said he didn't want a possible legal proceeding to be compromised because outside investigators were allowed onto a crime scene.

Coan said the Chemical Safety Board might be allowed onto portions of the explosion site no longer useful in a criminal investigation. And he expected the board would play an instrumental role in the investigation if it's determined the explosion wasn't a crime.

"Our intent right now, by statute of the commonwealth, is to finish our origin-of-cause investigation," Coan said.

Coan said investigators had made "significant progress" in their search to find a cause of the explosion. He said they had narrowed their focus to a "particular area" off the explosion site but would not provide more specific details.

Environmental Protection Agency officials could begin cleaning up portions of the explosion site later this week, Coan said.

Horowitz declined to discuss what options, such as going to court, the Chemical Safety Board might pursue if it's denied access today.

"The statute is pretty clear," Horowitz said. "We have the right to enter these sites, gather and subpoena documents and witnesses, and convene public meetings. We're fully prepared to exercise those rights."

Staff writer Paul Leighton contributed to this story. Matthew Roy can be reached at 978-338-2544 or by e-mail at mroy@ecnnews.com.

Returning to normal

Town Manager Wayne Marquis continues to provide daily 10 a.m. briefings and answer residents' questions at Town Hall. Part of his message yesterday was that things in Danversport were slowly returning to normal.

He reported that the streets had been swept and that a Dumpster holding spoiled Thanksgiving food had been emptied. In addition, curbside rubbish will be collected starting at 7 this morning, as is routine, Marquis said.

"We're trying to take baby steps toward normalizing life for the residents in that neighborhood," he said.