RESERVE — A man was killed after his RV caught fire in St. John Parish, the Louisiana state fire marshal's office said Tuesday.

The fire happened around 10 a.m. Monday on West 18th Street near La. 44 in Reserve, the state fire marshal said. A 67-year-old man living in the RV was pronounced dead at the scene.

While conditions were very cold at the time — 30 with a wind chill of 22 — investigators believe the fire may have been caused by a lithium battery, the same kind found in phones, laptops, e-bikes, power tools and most other modern rechargeable devices. According to the fire marshal's office, such batteries can become fire hazards if not charged safely.

The investigators also said the RV did not have a working smoke alarm. 

This marks the fourth fatal fire in Louisiana that the fire marshal's office has reported in the last week, resulting in a total of seven fire-related deaths.