The exterior and interior of the Old Town stable was damaged in the fire. View Full Caption DNAinfo/Paul Biasco

OLD TOWN — A suspicious fire that destroyed 13 horse carriages in Old Town earlier this month has been ruled an arson, Chicago Police confirmed Monday.

Following a lengthy investigation at the former Noble Horse Theater, police handed the case over to the FBI.

"It looks like further investigation resulted in, that it was in fact an arson. However, it is an ongoing investigation," said Officer Jose Estrada, a Chicago Police Department spokesman.

Police originally said the fire was not suspicious after their initial investigation on the morning of Feb. 6, but Estrada said a DNAinfo Chicago story detailing graffiti discovered at the site prompted further review the following day.

Owners of a number of the carriages that leased space at the stable, 1410 N. Orleans St., discovered bright green spray paint graffiti inside a hallway of the stable that read "Freedom" on one wall and "Free Save the Horses" on another after the initial police investigation.

More recently, investigators discovered bright green graffiti on the roof of the building with a similar message, according to Jim Rogers, owner of Great Lakes Horse and Carriage.

"Same words and pretty much the same handwriting," Rogers said.

Rogers kept both of his carriages at the stable, and both were destroyed in the blaze.

Rogers said there were also items found inside the barn that were not there the day before the fire started.

An FBI spokeswoman confirmed the bureau was investigating the arson, but declined to comment on details of the fire and any potential suspects.

Special Agent Joan Hyde, an FBI spokeswoman, said it is not uncommon for the bureau to participate in the initial stages of an arson investigation with local law enforcement to determine if there is FBI jurisdiction.

The fire broke out at the stable around 1:23 a.m. Feb. 6 and destroyed 13 carriages and damaged a significant portion of the exterior of the stable.

No horses were injured during the fire.

Rogers said the carriages cost about $10,000 to $12,000 apiece and are handmade.

The other 11 carriages that were destroyed were owned by Antique Coach and Carriage.

After the blaze, Rogers said he believed the fire was a "deliberate act" by "radical animal rights activists," adding that the stable has received threats from animal rights groups over the years.

Rogers said the horse carriage business is his and his wife's main source of income and that a friend is lending them two carriages while the fire is being investigated.

"We are working on" getting back up and running, he said. "We weren't able to work this past weekend because it was so cold."

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