For the second time in a month, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has called in a national team of investigators to determine the source of a Minnesota fire and whether arson may have been a factor.

The National Response Team arrived Tuesday at the scene of a fire in Grand Rapids that destroyed two downtown businesses last weekend. In the next few days, the 25-person team will work alongside local fire crews and law enforcement, digging through the rubble of the buildings, recreating the fire and helping to interview potential witnesses.

The team is made up of veteran special agents with "post-blast and fire origin-and-cause expertise," including forensic chemists, explosives enforcement officers and dogs that can sniff out accelerants such as gasoline, according to the ATF.

The ATF called in a national team last month to investigate the cause of the Press Bar and Parlor fire in St. Cloud. That investigation led to the arrest of bar owner Andy Welsh, who has been charged with intentionally lighting the fire that destroyed the building. Through recreating the scene, the investigators concluded that Welsh started the fire on his basement desk using some type of accelerant.

Before that incident, the ATF had not called in a National Response Team to Minnesota since 2004.

The Grand Rapids fire broke out around 9 p.m. Saturday, burning through the local VFW Post and Lake­view Behavioral Health office. It took firefighters all night to extinguish the blaze.

In a news release, ATF spokeswoman Ashlee Sherrill said the Grand Rapids Fire Department and Minnesota State Fire Marshal Division requested the extra help.

"ATF's National Response Team brings a wealth of knowledge and resources to assist local fire departments during investigations of large structure fires such as this," special agent William Terry Henderson of the St. Paul Field Division said in a statement. "The extra personnel will help move this investigation along more quickly. Our goal here is to assist in a full investigation of this fire scene alongside our state and local partners, bringing it to a successful conclusion."

Andy Mannix • 612-673-4036