For someone who has sold dirt bikes for 20 years, Mike Johnston thought he had his shop sufficiently fortified against break-ins: bars on windows, a video surveillance system and concrete barriers to deter a car crashing through the entrance.

But it turned out they were not enough in the spring, when thieves smashed into Ellicott City Motorsports in Maryland and made off with five dirt bikes — twice.

“The problem just keeps getting worse and worse,” said Johnston, whose store was struck two times in seven days. “It really is an epidemic.”

Johnston’s shop is one of several recently burglarized motorbike dealers along the East Coast who say thefts at their locations have ramped up in recent years. This is happening as swarms of illegal dirt bikes and all-terrain vehicles regularly flood public roads and pop wheelies in chaotic hordes, chasing social-media stardom.

In the D.C. region last week, nearly 100 dirt bikes and all-terrain vehicles choked traffic in downtown Washington and the National Harbor. Video posted on Twitter shows joyriders weaving around cars, driving against traffic and ignoring police attempts to pull them over. Police say the vehicles used in such spectacles are often stolen, from private owners and shops.

(Ellicott City Motor Sports)

Dealership thefts are becoming so common, shop owners from Pennsylvania to Virginia have created an informal network to alert each other of break-ins and share lookouts for suspected thieves.

“We immediately call and share what was going on with the break-ins,” said Johnston, who talked to owners of five dealerships burglarized in 10 days in late June. “We’re all trying to avoid the same problem.”

In May, thieves smashed the window of a Connecticut shop and stole $30,000 worth of bikes in about two minutes, the third break-in at the store in six months, according to local news reports.

[Dozens of illegal dirt bikes, ATVs choke the streets of National Harbor]

On June 25, a Pennsylvania shop lost $60,000 worth of bikes after someone crashed a van through the front door, “entered the store with precision” and stole seven motorcycles and scooters, according to police there.

And the week before, two men rammed a passenger van into the entrance of Powersports East in Delaware four times before busting through the entrance, said Pete Clarkin, the store’s finance manager.

“Watching it is extremely violent,” Clarkin said of the heist, captured on surveillance cameras. “When you walk through that door every day for work and then see someone drive a van through the door, it’s unsettling.”

Ellicott City Motorsports was burglarized twice in seven days. “The problem just keeps getting worse and worse,” said store owner Mike Johnston. “It really is an epidemic.” (Marvin Joseph/The Washington Post)

Through the rubble of shattered glass, and in under four minutes, the thieves carried out four dirt bikes and loaded them into the van, which had been stripped of its passenger seats, Clarkin said.

In six years, the Delaware store has lost 20 bikes in 10 burglaries, Clarkin said. The most recent break-in caused $300,000 in damage.

The vehicles are appealing because they are not connected to license plates that can be traced, said Lt. Craig Winegardner of Prince George’s police.

“They don’t require keys, and you can kick-start and ride away,” Winegardner said. “They’re easy to pick up and put in a pickup truck.”

Clarkin and others suspect that their stolen wares are making it to Baltimore, the Washington region and other bigger cities for sales and joyrides.

And as those dealers watch video of swarms of bikes rolling over curbs and around traffic, they cannot help but wonder if they’re looking at their own merchandise. “You see it, and your mind goes crazy,” Clarkin said.

Store owners say police do not always make arrests in such cases, and when they do, the recovered bikes are damaged and often cannot be resold.

But police have been cracking down.

In the District, police have arrested about 80 people and recovered more than 50 vehicles since launching a regional task force in 2016 to focus on groups of illegal ATVs and dirt bikes on public roads.

[In the shadow of the Capitol, outlawed dirt bikes take to the streets after dark]

In Baltimore — home of the infamous dirt bike pack the 12 O’Clock Boys, who became the subject of a documentary — the police department created a task force more than a year ago to deter mobs of riders who regularly buzz through the city and disturb residents. Of the 420 dirt bikes police have seized since the launch of the task force, 88 were stolen, said Baltimore Detective David Jones. Many of the stolen bikes have been ripped off from dealerships and private owners in the suburbs around Baltimore County and from as far away as Pennsylvania and Virginia.

Recently, when a Pennsylvania warehouse was burglarized and several dirt bikes were stolen, law enforcement in the area immediately contacted Baltimore police to see if the stolen bikes wound up in the city, Jones said.

“You have a small group of guys who do the burglaries to ride or sell to turn a profit,” said Jones, who added that those stealing the bikes are often connected with the hordes that disrupt city streets in packs.

Jones said the city’s crackdown has whittled the groups of riders — from 50 to 100 on a given Sunday to “a pack of maybe 20 at the most.”

John Ross, owner of Ride On Moto in Winchester, Va., said his sons recently had two dirt bikes stolen from a locked trailer in South Carolina. And two weeks ago, someone pulled the front door from Ross’s shop and made off with four bikes worth about $10,000 each.

Ross, who was out of town tending to his sick mother, watched the entire burglary unfold live on his phone when he got a remote alert about the early morning break-in.

Ross has added aluminum bars to his store and plans to install a fence around the building. He also parks huge trucks in front of the shop to deter thieves from plowing their own vehicles through the storefront.

“We’re just so used to it,” said Ross, who has been in the business for about 25 years. “You can’t stop them. You just have to slow them down.”

Ross said his insurance company has talked about increasing premiums for motorbike dealerships because of recent burglaries. And every theft costs him at least $2,000 to $3,000 out of pocket, in addition to the $30,000 he pays annually to insure the shop.

In the case of Ellicott City Motorsports, police tracked down the van that witnesses had spotted at the store’s second burglary.

The van fled from police and, after a short pursuit, broke down. Four teens inside escaped but were quickly apprehended.

Three 16-year-olds and one 15-year-old, all of Baltimore, were charged with burglary, motor vehicle theft, destruction of property, and fleeing and eluding, according to Howard County police.

Two of the teens were released to the custody of their parents, then arrested a second time shortly after in connection with a burglary at a scooter shop, according to Johnston.

Johnston said he spent about $40,000 to repair damage from the recent break-ins and for security upgrades.

Now even more bars fortify his shop. But there is a trade-off in how his shop feels to legitimate customers.

“Many customers don’t expect to walk around a place that looks like a prison,” Johnston said. “It’s not fair to the customers.”

Peter Hermann contributed to this report.