A welder reportedly might have caused a warehouse fire Tuesday afternoon.

Iowa City Fire Battalion Chief Brian Platz said in a letter to Chief John Grier that his team believes a welder could have started the fire.

The welder was doing work on a steel trailer inside one of the units.

Seven of the nine units in the warehouse suffered extensive fire damage, and the remaining two suffered watered damage. The damaged to the building was assessed at just under $1 million.

According to the letter, the initial crew witnessed at least five explosions. All occupants of the businesses were out of the building at the time of arrival, and there were no injuries reported.

Officials later found the building contained LP tanks, acetylene tanks, gas tanks, diesel tanks, and many paints and lacquers.

— by Rebecca Morin