Red chip Union Bank maintained its upward momentum yesterday, gaining 6.25 per cent to $17. Rumours persist that the company will receive an asset injection from its parent China Merchants Holdings. 'The rumours have been going for so long that there must be something to it,' one trader said. The stock has risen more than 50 per cent in the past two weeks. Another trader said he had put through a large order from the Hong Kong office of an international brokerage. Fellow red chip Ka Wah Bank edged lower after surging more than 18 per cent on Wednesday.