CHICAGO, Nov 12 (Reuters) - A fire at the office tower housing the Chicago Mercantile Exchange on Tuesday forced an evacuation but was not expected to disrupt trading when the markets reopen on Wednesday, exchange officials said. The blaze broke out inside a grease chute serving a ground floor restaurant in the southern tower of two that comprise the skyscraper, a Chicago Fire Department spokesman said. The fire occurred after futures trading had closed for the day. The CME houses pits for futures on stock indexes, interest rates, currencies and commodities. Pit trading was set to resume at 7:20 a.m. CST (1320 GMT). Most of the exchange's contracts are traded after hours on its Globex electronic system, which is computerized. "The Globex system is trading and there's no reason to believe we won't resume trading tomorrow," exchange spokeswoman Ellen Resnick said. Such blazes are typically confined to the metal "grease" chute that empties out from the structure's roof and they burn themselves out once starved of oxygen, the fire department spokesman said. A column of smoke from the top of the tower was visible from the ground. A building spokesman said many offices in the towers were evacuated, and the smell of smoke was noticeable in the lobby.