Social media is in part to blame for an apparent increase in the number of dirt bikes and all-terrain vehicles on urban streets, District of Columbia Police Chief Cathy Lanier said Thursday.

The Washington area has dealt with several recent cases involving off-road vehicles that have alarmed law enforcement officials and the public, including an officer who was injured when his motorcycle was dragged by an ATV and an ambulance that was blocked by several off-road vehicles last month. The ambulance was delayed in getting to a hospital, although no one was injured and the patient wasn't affected.

Also last year, a group of people riding off-road vehicles brought traffic to a halt on the Capital Beltway outside Washington while shooting video.

"I think for the riders this has become a trend where they videotape themselves," Lanier said at a news conference. "They're videotaping disruptions. For them, they think it's fun."

Lanier said police have seized nearly 400 dirt bikes and made nearly 100 arrests in the past year, but the trend of dirt-bike disruptions is expected to continue, especially as the weather improves. Police released photos on Thursday of 245 people believed to have been riding bikes illegally.

Dirt bikes have long been popular in Baltimore, where one famous gang, the 12 O'Clock Boys, was the subject of a 2014 documentary, and officials there are considering creating an urban park to give people a place to ride.

In New York City, Mayor Bill de Blasio this week announced plans to "crush" seized dirt bikes and broadcast the destruction on television. New York police reported that they'd seized more than double the number of illegal rides in the first quarter of 2016 than in the same period last year.

Urban dirt bikes pose enforcement challenges because the illegal rides make it easy for operators to elude officers. Police tend not to chase them because the pursuit can endanger more lives than letting the riders go.

"If a police officer in a police cruiser attempts to pursue these vehicles, what we know will happen because we've seen it happen is they will go up on the sidewalks and they will strike pedestrians," Lanier said. "We're not going to do that."

Dirt bike riders also face relatively light punishment if they do get caught. While police can impound and in some cases destroy the bikes, riding them on the street is a misdemeanor that usually leads to probation or a brief, suspended jail sentence for those who are convicted, said Karl Racine, the District's attorney general.

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