WASHINGTON (CBSNewYork/AP) — Residue from an explosive compound found at the scene of an explosion in a New York City neighborhood is unregulated and routinely used for target practice with exploding targets.

The compound, known by the brand name Tannerite, is sold in sporting goods stores. It is not regulated by the Bureau of Alcohol, Tobacco, Firearms and Explosives because it is sold as a mix of two chemicals that when kept separate are inert.

ATF has previously issued advisories about Tannerite and what it describes as “binary exploding targets.” The compound is typically used to mark a shot from a high-velocity rifle round with a small cloud of smoke.

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The explosive compounds are generally made up of an oxidizer such as ammonium nitrate and aluminum or another metal-based powder and only become an explosive when combined. The ATF said someone would only need an explosives license to handle the material if it is combined and they are using it commercially.

In a safety notice issued last year, the ATF said users of the compound should not use more of the explosive mixture than recommended by the manufacturer or use multiple packages of the compounds to make a single target.

The ATF also advised that once mixed, the compounds are “high explosives.”

Despite reports linking the bombings in New York City and Seaside Park, New Jersey, NYPD sources told CBS2 it is too early to tell if the devices are connected.

Sources said that there is no video or forensic evidence to support the theory that the same person was responsible for the bombing in Chelsea on Saturday night that injured 29 people and the pipe bombs in Seaside Park, New Jersey.

However, they have not ruled out a possible connection as both devices used cellphones as detonators, but that is common in explosive devices.

Mayor Bill de Blasio called it a bombing during a news conference on Sunday.

“This was a very serious incident, it’s going to take a lot of careful investigation to get to the facts and to the truth,” de Blasio said during a press conference Sunday afternoon. “We are not going to jump to conclusions.”

De Blasio said they do not yet know what the motivation was behind the bombing.

“This was an intentional act, but we do not know the motivation,” de Blasio said, adding authorities will be looking into whether it could have been politically or socially motivated.

De Blasio also called on New Yorkers to “be vigilant” and that there will be more police presence in the city.

“You will see a very substantial NYPD presence this week, bigger than ever,” de Blasio said.

WCBS 880’s Stephanie Colombini reported commuters saw more armed officers at Penn Station on Sunday.

“I feel like we’re used to it now. I mean like every time something like this happens that’s what they do, they put more cops on the ground with more guns,” Mike Iacano of Long Island said.

The NYPD said in addition to transit hubs, people can expect to see more police on the streets and at events like the United Nations General Assembly.

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