Egypt's stock market plunged almost 9 percent Wednesday, with foreign investors leading a sell-off in the market's first session in nearly two months following a shutdown linked to the mass protests that toppled former President Hosni Mubarak.

Traders said one of Egypt's best known companies, Orascom Telecom, accounted for roughly 30 percent of the turnover.

The benchmark EGX 30 index dropped 8.92 percent to close at 5,142.7 points. It has been closed since Jan. 27 and is now down 28 percent since the start of the year.

"Everyone was just selling," said Mostafa Abdel-Aziz, a senior broker at the Cairo-based Mideast investment bank Beltone Financial. "The foreigners were selling, the GCC (Gulf Arab) institutions were selling. Local institutions were mostly silent."

The reopening of the Egyptian Exchange — delayed several times — had been viewed with a mixture of trepidation and impatience. Analysts feared the prolonged closure would further unsettle already skittish investors. Some investors argued for its continued closure, arguing that the government needed to do more to offset their expected losses.

Men in a balcony above the trading floor dumped two bags of confetti on the brokers below to kick off the session. But less than 30 seconds later, trading was halted after a broad stock index fell below a threshold known as a "circuit breaker" designed to slow down sharp swings. It reopened 30 minutes later.

"We're urging people to hold on to their shares and not be hasty. You might regret it" if you sell, Finance Minister Samir Radwan told reporters shortly after the session opening which he oversaw along with the exchange's new, temporary head.

The reopening came a day ahead of a cut-off that would have left the Egyptian Exchange at risk of being de-listed from the MSCI Emerging Market Index, which is closely watched in relation to the more liquid developing world markets.

Analysts had expected sharp losses as investors pulled their money from the exchange amid ongoing investigations of former regime officials and some of the country's top businessmen whose companies are listed on the exchange.

Also weighing on sentiment were expectations that Egypt's economy would be hard hit as key foreign revenue mainstays like tourism and foreign direct investment suffered in the wake of the unrest.

"I was not surprised at all. It's something to be expected give the market was offline for seven weeks," said John Sfakianakis, chief economist for the Riyadh, Saudi Arabia-based Banque Saudi-Fransi, of Wednesday's plunge. "The situation in Egypt has not created confidence among international, and of course local, investors."

The call of holding onto the shares appeared to fall on deaf ears. Traders said even before the session, they were allowed to post their orders, and the sheer volume of sell orders undercut buying interest.

"I think the exchange made a huge mistake when they allowed investors and brokers to enter their orders before the session," said Abdel-Aziz. "Everybody began to offer their shares at the limit down."

"This discouraged buyers," he said. "When they saw this huge amount of sells, they simply preferred to wait."

Abdel-Aziz said Orascom Telecom, the Egypt-based telecommunications giant, was the key behind the EGX100 not hitting the 10 percent decline that would have frozen share prices at their limit-down level for the duration of the abbreviated session. OT's shares closed at 3.52 Egyptian pounds, dropping 2.76 percent, according to financial data provider Zawya.

Other blue chips, including investment bank EFG-Hermes, Orascom Construction Industries and the Commercial International Bank, spent much of the day trading at their lower limits.

OCI's shares closed at 204 pounds, down 10 percent. In a statement released by the exchange, the company said it wanted to buy back 750,000 of its shares, with a closing date for the purchase set at April 21.

The exchange's acting head, Mohammed Abdel-Salem, said that shares of 46 companies did not trade because they either failed to respond or didn't fully comply with information about their financial position.

Egyptian officials have ordered companies to make clear the holdings of officials and businessmen under investigation in a bid to ensure that those individuals are not unable to unload their stocks.

Abdel-Salem told reporters that the declines were "less than we expected" and pledged that it would not be shut down again.

Among the companies that saw trading in their shares suspended was Ezz Steel, whose head was a key member of the former ruling National Democratic Party, and Amer Group, a property developer that on Tuesday had said it would buy-back 101 million of its shares.

Radwan told The Associated Press additional measures may be put in place if needed.

"We'll do what it takes to have a safe opening," he said.

Sfakianakis said he believes the sell-off was "healthy" because too much selling pressure had been built up due to the market's prolonged closure.

"Steam has to be released," he said, adding that further declines are likely in the coming days.