Smoking was the cause of a fatal fire that took the life of a 70-year-old resident of St. Anthony's Manor last month.

"Investigators with the Casper Fire-EMS Department have determined the cause... to be smoking in close proximity to a supplemental oxygen device," Firefighter Dane Andersen said in a statement Wednesday.

The cause of death for Sharon Lee Marzocca, who died in the March 1 fire, remains under investigation by the Natrona County Coroner's Office.

Also in Wednesday's statement, Andersen said the cause of the fire at Alpenglow Natural Foods remains under investigation.

Investigators from private insurance companies are working with investigators from Casper Fire-EMS as well as the Natrona County Fire District to determine the initial source of the blaze.

"Due to concerns of the presence of asbestos in the building, further investigation had been temporarily delayed while the threat was abated," Andersen's statement continues. "As of the time of this release, cause determination is pending corroborated findings of all parties investigating the blaze."

Casper Fire-EMS emphasizes that "there is no safe way to smoke in the home when oxygen is in use." Anyone using supplemental oxygen should not smoke.

Candles, matches, wood- and pellet-burning stoves, even sparking toys can be ignition sources, and should not be used.

Oxygen cylinders and concentrators should be kept at least five feet away from any heat source, open flame or electrical device.