Nearly a dozen fires broke out in a matter of hours in St. Paul early Monday, and authorities think they were intentionally set.

The St. Paul Fire Department says all of them seemed to be happening in alleys behind homes and businesses, in a five-hour window. There were no injuries.

"Midnight to 4:30 in the morning doesn't fit the window of child fire play. This is potentially an individual. These could be isolated events, or they could be connected," said fire department spokesperson Roy Mokosso.

He said there were no witnesses to how the fires started but investigators are hoping they can still track down who might be responsible. Most of the fires were in garbage carts, but a shed and a play structure were also damaged, according to posts in a neighborhood Facebook group.

Fire officials estimated the damage in the tens of thousands of dollars.

This is one of nearly a dozen fires St. Paul fire officials say were deliberately set early Monday morning around the city. Courtesy of St. Paul Fire Department

Mokosso said investigators were particularly concerned that the location and timing of the fires made them vulnerable to spreading to homes where people were sleeping, potentially leading to injuries or fatalities.

Fire officials are asking people who may have noticed a fire on their property that had gone out early Monday, and didn't call 911, to contact the fire department at 651-224-7811 to report the damage.

Mokosso said they were also hoping surveillance footage might have captured someone starting the fires, and are asking businesses and homeowners in the Macalester-Groveland and Merriam Park neighborhoods to check their cameras or video feeds between midnight and 5 a.m. on Monday for anything suspicious.

There were also a number of fires reported behind University Avenue businesses between Snelling Avenue and Dale Street.