Firefighters from a specialist decontamination team removed radioactive substances from a van after it collided with a lorry on a motorway.
Oxfordshire fire service said “low levels” of radiation were detected leaking from the van after the crash between junctions five for Stokenchurch and six for Lewknor on the M40.
The van driver was taken to hospital after being checked for contamination.
The crash temporarily closed the M40 in both directions at about midnight.
Andy Ford, station manager for Oxfordshire fire service, said the incident was “potentially very hazardous”.
“Our initial priority was to rescue the driver, which was carried out as quickly as possible ensuring emergency personnel were not near the van for very long,” he said.
Mr Ford said firefighters in breathing apparatus and gas-tight protective suits were able to “identify the type of radioactive materials being transported” and “record the levels of radiation being emitted”.
“Because the levels of radiation detected around the van were significantly above normal, the area had to be cordoned off to await specialist containment and recovery,” he added.
The incident was handed over to Thames Valley Police to arrange recovery of the van and its contents, the fire service said.