Emergency crews spent about seven hours removing explosive and radioactive materials from a Lexington home on Tuesday, after a property clean-out uncovered dozens of unstable chemicals left behind by a deceased chemist.

What happened.

The operation at 23 Longfellow Road involved eight agencies, including the Lexington Fire Department, the Massachusetts State Police Bomb Squad, an FBI bomb technician, and the state Department of Fire Services' hazmat division. No one was injured, and officials confirmed there was no criminal activity.

What crews found.

Firefighters arriving Tuesday afternoon identified picric acid, a highly explosive chemical, among dozens of bottles of liquids, powders and solids inside the home. Many of the substances were old, degraded and unstable; others were radioactive. "We found numerous substances within the home that posed a fire or explosive hazard," said Lexington Fire Chief Derek Sencabaugh. "These materials could not be left in place and had to be carefully and methodically removed for safe disposal."

How the removal worked.

Lexington Police secured the perimeter while an engine company stood by with charged hoselines and EMS crews staged nearby as a precaution. Bomb technicians in protective gear moved the explosive and unidentified substances into a sand-filled Department of Public Works truck, which then transported the materials to a remote location where they were safely destroyed. A licensed radiological contractor took custody of the radioactive materials, and a private cleanup company handled the rest. Crews cleared the scene by about 8 p.m.

How common is this?

State Fire Marshal Jon M. Davine said his agency handles similar situations a few times a year, often when family members find military ordnance after a veteran dies. He called the Longfellow Road case "a much more complex scenario" that "required patience, precision, and a high degree of technical skill." The Massachusetts Department of Environmental Protection also responded. Officials did not disclose the identity of the deceased chemist.

Disposing of hazardous household chemicals.

Lexington residents can use the Minuteman Household Hazardous Waste Products Regional Facility at 60 Hartwell Avenue. The next collection date is Saturday, Aug. 15.