Some residents in Windsor and Detroit were surprised by a fireworks display that filled the sky with explosive colours above the Detroit River on Wednesday evening.

The event, set on the river between the two cities, started at 10 p.m. and continued for about 17 minutes.

Unlike the much-publicized Ford Fireworks display that draws spectators from Detroit and Windsor to the riverfront, this show wasn't widely advertised.

"We don't want to have a really large crowd down there because it complicates crowd control measures, security and everything else that's necessary," said Aaron Enzer, president and owner of ACE Pyro, the company that put on the show.

Enzer said the private show was held for an insulators union convention in Detroit.

"Private events like this usually are not advertised, although obviously people that love fireworks would love to know about it," he said.

WATCH | More on Wednesday night's fireworks display: 

Enzer acknowledged that his company's display did not intend to irritate or cause distress to people on both sides of the river.

"We are very sympathetic to animals," he said. "I have two dogs myself that don't always enjoy fireworks as much as I do, and to that, we apologize. I understand catching people off guard with the fireworks."

Windsor's harbour master Peter Berry took issue that the local Port Authority was not notified of the display.

"I spoke with [the United States Coast Guard] this morning and it was acknowledged that the communication did not get sent by error. However, notice to ships was broadcast, closing the U.S. side of the river during the fireworks show," Berry said, in an e-mailed statement to CBC News.

Some residents took to social media, expressing their surprise to the un-publicized show.

"Thanks for the very alarming fireworks show [in] Windsor," tweeted Ciara Lowe.

A public affairs officer with the United States Coast Guard (USCG) told CBC News they did alert the Canadian Coast Guard detachment in Sarnia.

The USCG said after it was notified of the event, they confirmed the company had all the proper permits, and set up a safety zone on the U.S. side of the Detroit River around the fireworks launch point, which was a barge on the river. That lasted from 9:30 p.m. to 10:30 p.m. Wednesday, and the public affairs officer confirmed there was no significant impact on commercial traffic on the Canadian side of the river.