DOYLINE, La. — Authorities slowly moving 6 million pounds of explosives improperly stored at a munitions recycling facility feared a chain reaction blast could have spread because corridors connecting storage buildings were packed with explosive materials, the sheriff of the threatened area said Tuesday.

A voluntary evacuation order for Doyline, a town of 800 people near the site and about 25 miles east of Shreveport, was expected to remain in effect until at least Friday as the material was moved to a safer location elsewhere on the sprawling Camp Minden grounds.