ST. LOUIS -- A neighborhood on the city's north side was transformed Saturday when about 100 firefighters responded to nine blazes within two hours, and fire investigators said at least the first six fires were set.

Police had a suspect in custody, fire chief Sherman George said.

Kim Bacon, a Fire Department spokeswoman, said no injuries were reported.

"Nothing like this has ever happened in St. Louis in the 15 years that I've been here," said resident Craig Williams, 38.

To his left, there were fire trucks one street over. To his right, dark, thick smoke billowed from a two-story vacant brick warehouse on Jefferson Avenue. The blaze was elevated to four-alarm status around 6:30 p.m.

The warehouse was under contract to be demolished, George said.

Firefighters fought the warehouse blaze from outside of the structure, surrounding it with ladder trucks as arcs of water cascaded into the building.

Streets on the perimeter of the neighborhood were temporarily shut down, and the entire neighborhood was lit by the flashing lights of fire trucks spaced about a block apart. Clusters of neighbors stood outside, watching the commotion in disbelief.

Bacon said the first call came in at 2:52 p.m., and others followed shortly thereafter within an eight-block radius.

"They've been consecutive -- boom, boom, boom," she said.

By Saturday night, at least 20 engine companies helped to fight the fires. The six buildings where arson was suspected were all vacant, George said, and apparently had their utilities turned off.

"Fires don't get started by osmosis," he said. "There was no gas, no electricity. They're suspicious."

Williams and his neighbor William Holmes, also 38, said they left their apartments shortly after 3 p.m. to wash their cars.

"The next thing I know, I heard an alarm and I started seeing smoke in two directions," Williams said.

The two said their neighborhood is home to several abandoned buildings.

"You could put a circle around this area and see where there's been all these fires," Holmes said, gesturing around the neighborhood while standing outside his home.

He wondered if he'd have trouble letting his guard down to sleep. "I'm going to be looking out my window tonight."