Several people of interest in New Berlin pipe bomb explosions

WAUKESHA COUNTY, Wis. (CBS 58) -- Authorities have released new information about two explosives that went off last month in New Berlin. 

According to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), they were pipe bombs. 

It happened along rural Coffee Road.

The two explosive devices detonated in September. The first was in the early morning hours of Sept. 15, the second was Sept. 17 in the afternoon.

Neighbors tell CBS 58 news they heard the blasts. "Boom! It just went off, just like a big firework," said George Bader.

The ATF said they're investigating several people of interest.

While no one was hurt, they said  the situation could have been a disaster.

"It could've been catastrophic. A pipe bomb is a very dangerous device...it could be devastating for a person, because a pipe bomb has several components that can cause extensive damage," said Joel Lee, Assistant Special Agent.

Federal investigators continue to ask the public for information. They are offering up to a $5,000 reward for information on the case.

They add if you ever come across what you suspect is a bomb -- call 911 immediately.