A seven-hour hazmat operation at 23 Longfellow Road in Lexington on Tuesday, July 21, cleared a deceased chemist's home of picric acid, radioactive materials, and dozens of unstable chemical bottles, fire officials said.

The Lexington Fire Department, State Police Bomb Squad, and Massachusetts Department of Fire Services worked together to remove the substances after a private contractor hired by the property owner called for help. The contractor found materials that were "beyond their scope," Lexington Fire Chief Derek Sencabaugh told the Lexington Observer.

Firefighters arriving around midday identified picric acid, a highly explosive chemical, among dozens of bottles of liquids, powders, and solids, according to the state Department of Fire Services. Many were old, degraded, and unstable. Others were radioactive.

The home had been unoccupied since the resident, a chemist, died. The Department of Fire Services said there was no indication of criminal activity.

Lexington Police secured the area around the home while EMS crews staged nearby as a precaution. An engine company stood ready with charged hoselines as specialized teams entered.

Hazmat and bomb technicians systematically examined the home, separating materials by hazard type. State Police bomb technicians, wearing full protective equipment, transferred the explosive and unidentified substances into a Lexington Department of Public Works truck filled with sand.

Those materials were transported to a remote location and destroyed without incident. A licensed radiological contractor took custody of the radioactive substances, and a private cleanup company handled the remaining materials. Teams cleared the scene by approximately 8 p.m.

"We found numerous substances within the home that posed a fire or explosive hazard," Sencabaugh said in the Department of Fire Services press release. "These materials could not be left in place and had to be carefully and methodically removed for safe disposal. Our priority at every step was the safety of community residents and our first responders."

State Fire Marshal Jon M. Davine said his agency sees similar situations a few times a year, often involving family members who discover military ordnance after a veteran dies. This case was far more complex.

"It required patience, precision, and a high degree of technical skill," Davine said.

The full roster of responding agencies included the Lexington Fire Department, Lexington Police, the Massachusetts Department of Fire Services Hazardous Materials Emergency Response Division, the State Police Bomb Squad, an FBI special agent bomb technician, the DFS Joint Hazard Incident Response Team, the Massachusetts Department of Environmental Protection, and a DFS Rehab Unit.

Residents who discover unknown chemicals or suspicious materials in a home should not attempt to move them. Contact the Lexington Fire Department or call 911.