The London Stock Exchange was back in business Tuesday after a Monday outage that lasted almost an entire day. The LSE electronic trading system was taken off line Monday approximately 45 minutes after trading began and service was not restored until 16:30 (BST). The exchange is not revealing the reason for the problems, although it said the cause has been identified and a fix put in place. A spokeswoman did say that the problem was software related and was due to two "unpredictable events" occurring simultaneously. Trading was resumed after the fix went in and trading is now back to normal.