The massive blaze erupted in the decrepit Whispering Pines Motel last week not far from a sign advertising a $25,000 reward for tips on one of the worst arsonists in Virginia history.

The person torched a shuttered restaurant the next night and burned an old schoolhouse to the ground Thursday, slipping away into the darkness long before anyone even knew the fires had been set.

The relentless series — more than 70 arsons — has sent flames shooting into the sky over this rural Eastern Shore county about every other night since mid-November and created a deepening urgency and mystery with each new spark.

The culprit or culprits seem to be taking great care to evade detection. Virginia State Police said the fires have been set in ways that they go undetected for an hour or two, although authorities declined to discuss those methods. Officers said the burned buildings, although scattered across the 450-square-mile county, are in areas with multiple escape routes.

“Whoever is doing this is really doing their homework,” said Ron S. Wolff (I-District 2), a member of the Accomack County Board of Supervisors.

(Virginia State Police)

Federal, state and local authorities have launched a major investigation, rushing to make an arrest before a fire turns deadly. Meanwhile, residents are on edge, and some see signs the fires are escalating.

Among residents, speculation about the arsonist and the motives for the fires swirls. Many say they think the carefully planned blazes point to someone familiar with firefighting or law enforcement or perhaps someone who has served in the military. Some say they think the arsonist could be someone angry with the county for not doing more to clean up blighted properties. Others entertain theories such as the government is using drones to blow up the properties.

On Friday afternoon, Ann Mills surveyed the smoldering remains of the old Cashville schoolhouse, which her husband used to store farm equipment.

“Three nights in a row. I would just like to know: Why?” Mills said. “I just don’t like that it’s getting bigger and bigger.”

The arsons have largely struck abandoned and dilapidated buildings that line the twisting country lanes in this old agrarian community. But some have hit properties such as the once popular Whispering Pines, which closed years ago and is emblematic of the area’s economic struggles. Accomack is among the poorer counties in Virginia and has lost 13 percent of its population since 2000, according to U.S. Census figures.

Those factors have created a ready tinderbox: Officials estimate there are 700 abandoned buildings in the county.

Fire in the night

Lois Gomez said she awoke about 3 a.m. to a loud banging on the front door of her Parksley home the night the arsonist struck. “Your garage is on fire!” a neighbor screamed.

Gomez and her husband rushed outside to find flames leaping from the back of their detached garage, about 20 feet behind their home and near a large propane tank. It was too late: Flames quickly incinerated $50,000 worth of items and irreplaceable keepsakes.

Gomez said the arsonist had crept into the back yard quietly enough that the dogs of neighbors on both sides of her house never barked.

“It was like he dropped out of the sky,” Gomez said.

But there was one aspect of the Dec. 15 fire that was even stranger: Gomez said the coop adjoining her garage had been opened, allowing her chickens to escape the blaze. She said she thinks the arsonist intentionally let them out.

If true, it would fit with one aspect of the arsons. Police said that all of the structures targeted have been vacant and that no person or animal has been harmed. Authorities said they think the arsonist might be watching the buildings to see whether anyone is around.

All the fires have occurred at night, with about 70 percent sparking between 6 and midnight, police said.

Evidence collected from fire scenes and the fact that multiple fires have been set within a short time lead police to think that most of the arsons have been committed by several people, possibly working in connection with each other. They said they think a few of the fires are copycat arsons.

The state police have responded by deploying extra officers and a plane, setting up checkpoints and using cutting-edge “geospatial predictive analytics” technology that helps guess where the arsonist might strike next based on previous behavior. Officers have spent about 18,000 hours on the case, police said.

“We have developed several strong leads as to who may very possibly be behind these fires,” state police Capt. T.A. Reibel said in a statement released last month.

No arrests have been made, though.

Pushed to the brink

On Friday evening, Onley Fire Chief Bill Ferguson girded himself for the possibility of another long night. The three previous nights had produced three arsons — enough to push his volunteer force of 20 firefighters to the brink.

Unlike professionals, they had to wake up and go to full-time jobs after spending hours battling blazes each night. Ferguson had dark circles under his eyes as he waited for the next call at the fire station.

“We’re tired,” Ferguson said. “But the guys and gals have rallied.”

The Onley fire department had responded to 15 arsons as of Friday night. That was about the same number of fires it responded to in all of 2012.

The arsons have touched firefighters personally. In January, they were called to put out a blaze that had burned a hangar on the property of Onley’s former fire chief, who had recently passed away.

The story is similar up and down Accomack County, which relies on a majority-volunteer force of 600 firefighters. Crews are stretched thin, and firefighters are worn out and hoping the next blaze does not strike when they have another emergency to attend to.

The only consolation has come from an outpouring of donations of coffee, water and desserts from the public to fuel them each night.

Dian Williams, founder of the Center for Arson Research, said arsonists generally fall into a number of categories. They include revenge arsonists, who use fire to punish people who have slighted them, and thrill-seekers, who enjoy getting away with setting fires and sowing fear in a community. Regardless, she said, arson is one of the most “underprosecuted” crimes.

“It’s a deeply hidden crime — often by the time an arsonist has been arrested, they have been setting fires for years,” Williams said. “There are often no witnesses, and many arsonists feel no sense of guilt, so they are unlikely to turn themselves in.”

The one thing that baffles and troubles most residents is that the arsonist has operated for four months without anyone coming forward with a tip to break the case. Everyone describes the county of 33,000 residents as “tight-knit.”

“We’re known for helping each other in bad times and for knowing each other’s business,” said Beth McGlothlin, an Accomack County resident.