A fire broke out at a Roma migrants' camp in Fresnes town in central France, near Paris, late on Tuesday night, local media reported.
The fire started around midnight, daily Le Figaro reported, adding that firefighters were dispatched to the scene.
A total of 150 people, including many children, have been evacuated from the camp in less than 30 minutes.
Two hours later, firefighters found a woman's burnt body under the debris, Le Figaro said, citing a police source.
Her 33-year-old husband was standing not far from her with a long kitchen knife in his hand.
Police officers arrested and took him into custody.
Witnesses explained that the 39-year-old woman was regularly subjected to her husband's "acts of violence," Le Figaro added.
An investigation is underway for "murder by partner, voluntary destruction by fire, and modification of the crime scene to obstruct the truth."
