An uprising in Egypt which started two weeks ago has paralyzed the country, as protesters demand an end to President Hosni Mubarak's three decades of rule.
Egypt's main stock market index is down 21 percent this year and its financial markets have been shut for eight working days.
However, builder Construction Products Holding Company (CPC), an affiliate of conglomerate Saudi Binladin Group, is standing by Egypt.
"The Egyptian market has great importance for CPC's investments," said Faisal Ibrahim Al-Aqil, director of business and administration affairs development.
"The board is confident and optimistic the crisis will be resolved soon and things will go back to normal."
Investment firm Abdul Muhsin Al Hokair Holding, which invests in shopping malls and other services, said it would stick to its investment plans in Egypt despite a fall in its business there of between 30 and 40 percent in recent days.
"Our strategy and work is continuing. We have great confidence in the Egyptian market," said chairman Abdul Muhsin Al Hokair.
Some Saudi companies are less optimistic, however, such as travel agency Al-Tayyar Group, which has some 100 million riyals ($26.67 million) of investment in Egypt.
"Our operations declined by nearly 30 percent," said Nasser Al-Tayyar, the firm's president.
"We are seriously thinking of not paying salaries if the crisis continues."
Saudi Arabia is one of Egypt's biggest trade partners and Saudis are leading investors in its stock market, tourism, aviation, real estate and agriculture sectors.
Some two million Egyptians live and work in Saudi Arabia.
Saudi investments in Egypt are estimated at $4.6-5 billion, said Abdullah Dahlan, head of the Saudi-Egyptian Business Council, adding some companies working in Egypt expect their production to run at lower capacity for several months.
