The affected suites run from home plate down the first base line at the 10,000-seat ballpark, which is home to the West Michigan Whitecaps, a Class A affiliate of the Detroit Tigers.
A few workers were in the ballpark's offices when the fire started in one of the suites. No injuries were reported.
The response to the fire was slowed by a lack of fire hydrants near the park, said Plainfield Township Fire Chief David Peterson. He said firefighters had to extend hoses to other hydrants, 1,500 feet away, which created low water pressure.
Firefighters from Plainfield Township and other Grand Rapids-area departments, out in single-digit temperatures, took a defensive approach shortly after arriving at about 11 a.m. Thick, black smoke rising from the ballpark was visible from miles away.
"It was really kind of nasty," Peterson said, describing the conditions firefighters faced.
He said the structure on the first-base side was "pretty much destroyed."
Peterson told WZZM-TV that the fire was sparked by a space heater being used by a work crew at the ballpark.
The fire chief said the construction crew was working in a suite Friday morning when the heater caused a small fire. The construction workers thought they had extinguished the fire, but flames kindled in the attic and quickly spread throughout the first base concourse.
Steve Reed has brought his family to many Whitecaps games. The Cedar Springs man said he wonders what will happen this summer.
"This is our summertime, and it's burning up right now" said Reed, who drove from his home to see the fire after hearing about it through the media.
Opening day at Fifth Third Ballpark is about three months away. Denny Baxter, the West Michigan Whitecaps managing partner, told WZZM-TV that he is confident baseball will be played there this year.
"We will rebuild. We will play baseball this spring," he said.
Fifth Third Ballpark, which opened in 1994 as Old Kent Park and changed to its current name in 2000, is scheduled to host the 50th Midwest League All-Star Game in June. It also has hosted concerts and high school football games. During the holidays, a Christmas light display is set up in the parking lot.