The Milwaukee Fire Department and its Hazardous Material Team were on the scene of a chemical explosion for over seven hours this morning.    There was a report of an explosion around 12:53 a.m. in the area of South 5^th Ct and West Rosedale Avenue.  The explosion occurred at 2829 S 5^th Ct, Milport Enterprises Inc.    According to Milwaukee Fire Department officials, two non-toxic, non-hazardous chemicals inadvertently were stored together and a reaction occurred, building up pressure in the container which exploded, blowing the top of the container through the roof of the building.  The Fire officials say there were no hazardous fumes, there was no fire and no one was injured as a result of the explosion.  Fire officials said that, due to the nature of the call, they conducted an extremely methodical search of the building to ensure everything was safe and finally left the scene around 8 a.m.    Police had cordoned off the area to allow the Hazmat team to conduct its search.   A dollar estimate of the damage to the building was not available.