ANNISTON, Ala. (AP) – The Army on Sunday began burning about 800 gallons of deadly sarin drained from rockets, marking the most dangerous phase of its weapons incinerator use since the process began here Aug. 8.

The burn was expected to be completed around midnight, Army spokesman Mike Abrams said.

Sarin, also known as “GB,” is a nerve agent so deadly a drop on the skin can kill. The chemical was drained from 900 M55 rockets that have been chopped up and burned since the incinerator began operating on Aug. 8.

Forty to 42 gallons of nerve agent residue already have been incinerated at the Anniston Army Deport, but always in small amounts. Sunday marked the first mass burning of sarin and completes the destruction of the rockets at the Army’s newest weapons incinerator.

Sunday also was the first time the Army has burned a large amount of nerve agent near a populated area. Emergency planners say some 35,000 people live within nine miles of the incinerator.

The Army’s other incinerators are in more remote locations: Johnston Atoll in the Pacific Ocean and in the desert near Tooele, Utah. Another incinerator is being tested at Pine Bluff Arsenal near Pine Bluff, Ark., a city of about 55,000, and is expected to begin burning chemical weapons late next year.

Last week, officials in Anniston halted operations for two days to check the incinerator’s alarm system after two false alarms and an alarm when a small amount of GB vapor was detected in a room containing a secondary burner.

Abrams said there was no danger to the community or incinerator workers.

“It was at all times under engineering controls and there was no requirement to alert any emergency management agency office,” Abrams said.

He said officials “changed the process just a tad and took care of that situation” that caused the vapor leak.

The incident did not need to be reported to emergency agencies because the vapor did not escape from the exhaust stack, Abrams said.

Scientists with the Alabama Department of Environmental Management who have been at the incinerator since the burn operation began were satisfied that the other two alarms were false, said Stephen Cobb, chief of the hazardous waste branch.

Cobb said monitors that are so sensitive they can pick up trace amounts of sarin also can be easily triggered by other chemicals, including diesel fumes from passing trucks.

Incineration opponent Craig Williams was skeptical about the Army’s claims that the leaks were false alarms.

“It’s always amazed us that they can’t tell you what, they can’t tell you where, and they can’t tell you what triggered them, but they can always tell you it wasn’t agent,” Williams said. “And that really isn’t an acceptable representation.”