DUBAI, April 17 (Reuters) - Financially troubled construction company Saudi Oger sold a 2.8 percent stake in Saudi Investment Bank, bringing its stake in the bank down to 5.8 percent in the course of a single trading day, stock exchange data showed on Monday.

The data did not reveal the identity of the buyers and the companies could not immediately be contacted for comment.

Saudi Investment Bank, which offers retail, corporate, treasury and asset management services, had a market capitalisation of $2.62 billion at the market's last close, implying the sale could have raised about $73 million.

After dominating the Saudi construction market for years, Saudi Oger, owned by the family of Lebanese Prime Minister Saad al-Hariri, is struggling because of cuts in government spending and payment delays.

The company is awaiting the outcome of a government-commissioned review of its billions of dollars of projects in Saudi Arabia, which could help determine its future, banking sources told Reuters earlier this month.

(Reporting by Celine Aswad; Writing by Andrew Torchia) ((andrew.torchia@thomsonreuters.com; +9715 6681 7277; Reuters Messaging: andrew.torchia.thomsonreuters.com@reuters.net))