WAUKESHA, Wis. (CBS 58) -- The Waukesha Fire Department is investigating what caused an explosion at Airgas located on Sentry Drive.

Joe Hoffman, assistant chief of the Waukesha Fire Department, said around 1:42 p.m. Thursday, firefighters responded to the gas company. Officials with Airgas identified an explosion in the hydrogen storage area of the plant. 

Airgas employees identified a number of small cylinders that were leaking, and firefighters quickly put out a small fire in the area, according to Hoffman.

Officials originally told CBS 58 there were no injuries. However, in a press release, Hoffman said Waukesha Fire treated one Airgas employee at the scene and the employee refused further treatment.

"We were inside the office and (heard) a very loud explosion. Our mechanic said it sounded like a bomb from when he was in the war," said Pat Hannon, operations manager at Bryce's Lawn Service, the business next door to Airgas.

Sentry Drive from College to Sunset was temporarily closed, but all roads are back open now. No neighboring businesses had to close.

The cause of the fire is still under investigation.

This is a developing story. Stick with CBS 58 on-air and online for updates.