The emergency services launched a major incident operation after a man was blown up in his car today.
The 58-year-old died after the blast on Old Cemetery Lane, Hartlepool, Teesside, blew the roof off his Nissan Micra in the early hours.
Three ambulance crew members and two police officers who were first on the scene were decontaminated after suffering sore throats. All have been released from hospital.
Detective Superintendent Gordon Lang told a news conference in Hartlepool that it was not believed to be terror-related.
Mr Lang said a 250m cordon will be placed around the dead man's home to allow a search of his property to be safely carried out.
The man, whose family has not been traced, lived in a flat in Hartlepool Marina.
Boats moored there and people living in a nearby block of apartments will be evacuated.
Mr Lang said decontaminating the emergency services personnel involved simply washing with soap and water.
Detailed chemical analysis of the car and any substances in his home will take place later.
"This is highly unusual and as a consequence of that, it will be of concern to members of the public," he said.
"The experts are here and we dealing with it in a systematic and methodical way."
The detective said 25 police officers and five Army bomb disposal experts were working on the case.