The small, smoky fire burned only a short time in the Minneapolis Police Department's property room last month, but its path of destruction could have long-term results.

By the time the flames were out, more than 24,000 pieces of evidence secured in manila envelopes had been damaged or destroyed. But quick and creative action by firefighters and property room staffers saved shelf after shelf of additional investigative work.

The fire, discovered when nearby 911 operators smelled smoke about 1 a.m. on April 13, most likely was started by a faulty electrical connection in a fluorescent-light fixture in the property room subbasement.

The damaged evidence included photo lineups, small weapons, surveillance and police-interview CDs, sexual-assault kits, and crime-scene samples. No guns, drugs or money was harmed.

The Hennepin County attorney's office said that at least five cases have been affected by the fire and that more are likely to be in the coming months. Two weeks ago, property and evidence unit supervisor Kerstin Hammarberg testified in court about a valuable piece of damaged evidence that won't be produced at a trial.

"This is the first fire in the 15 years I've worked for the property room, and my staff was dynamite in preserving and cleaning it up," she said. "We are just lucky nobody got hurt. I recognize the evidence is important to criminal investigations. [But] in the end, it's just stuff."

Police guarded the property room during cleanup. Hammarberg said she's confident that staffers have inventoried almost all of the damaged property and that supplemental reports are being added to affected case files.

The fire-damaged evidence is connected to investigations over a period from late 2013 to last month. Some damaged evidence linked to cases being handled by the county attorney's office — such as documents, a box cutter, a cellphone and a utility knife — could be reproduced or wasn't pivotal. But a destroyed video could cause a problem, the office said.

The fire also raised concerns for Mary Moriarty, chief public defender for Hennepin County, whose office handled more than 45,000 cases last year. She said her office contacted the property room staff about evidence damage and received little information. Her office was told to make case data requests through prosecutors — a process that Hammarberg and Hennepin County Attorney Mike Freeman said was in place before the fire.

Prosecutors are obligated to disclose information that could be favorable to the defense. Because evidence in property rooms is within the domain of the prosecution, Moriarty said it should be proactive in providing defense attorneys with information about damaged evidence.

"It's frustrating for us to have to ask for this on a case-by-case basis," she said. "I understand it's a huge nightmare for the prosecution. I could come up with scenarios about how this evidence could impact a case, but we don't know what was damaged."

The property room protects millions of pieces of evidence, Hammarberg said. Only about 1 percent of it is checked out and presented in court, while 10 percent is tested by the state Bureau of Criminal Apprehension or the Police Department's crime lab. Some of the damaged property already had backup copies or test results stored with another agency.

"The department's ability to sort through the damage and salvage as much evidence as possible is a testament to the level of detail and professionalism that our Property and Evidence staff put forth every day," said Deputy Chief Travis Glampe.

Some damaged evidence could be critical to a person's right to a fair trial, said defense attorney Ryan Pacyga. When the prosecution has physical evidence in a case, the defense has the right to examine and run its own testing on it. He said he has seen cases where defense and prosecution lab results on the same evidence have come back differently.

Damaged evidence also could lead to pretrial suppression hearings, where attorneys argue that it should be thrown out, he said.

An extensive rescue effort

When Hammarberg got the call about the fire from a police watch commander, she rushed to City Hall and waited nervously for 1½ hours until firefighters told her it was safe to enter the property room.

Sprinklers knocked down most of the fire, which burned three shelving units full of 9-by-13-inch evidence envelopes. Water damaged five other shelving units, and hundreds of guns in cases on the ground had to be swiftly moved because more than 2 inches of water flooded the floors.

Crime-scene precautions kicked into gear, and Hammarberg and firefighters talked at length before anything was removed.

Hammarberg already had a disaster plan in place. She alerted police precincts to hold onto and secure evidence that they had planned to bring to the property room. Several community service officers training to become licensed Minneapolis police officers were designated to help clean the property room. The Minneapolis Fire Department deployed sump pumps to get rid of the water.

All burned evidence was photographed and documented. Wet evidence was taken to a police warehouse and placed on huge sheets of paper in the order in which it was found. Fans were brought in to dry it. "Everybody was very careful to make sure the chain of custody wasn't compromised," Hammarberg said. "We are the best baby-sitters. The evidence sits with us. We protect it. That's our charge."

She said her unit is likely to start receiving calls in the next six to eight months seeking affected pieces of evidence for cases going to court.

Meanwhile, burn marks remain on the property room wall, and the smell of smoke lingers. Temporary lights have been set up. New shelves have been ordered.

"Anything that happens to the property room is very personal to me," Hammarberg said. Part of her pride is the fact that Minneapolis had the first police property room in the United States accredited by the International Association for Property and Evidence.

Although April's fire was contained to a narrow, 20-foot space and the cleanup was as thorough as possible, it is likely to affect some cases, she said.

"You can't put a dollar value on the stuff that was lost," she said. "The value [could be in] proving a case up or down."

David Chanen • 612-673-4465