Stocks lost ground after the FBI announced new inquiries into the private email server of Democratic presidential nominee Hillary Clinton. (Reuters)

Investors rushed to sell their assets in equity and currency markets Friday afternoon after the Federal Bureau of Investigation said it was looking into Hillary Clinton's emails again. The revelation seemed to cause fluctuations in prices for a range of securities and commodities in the United States and overseas.

Shares in the Standard & Poor's 500-stock index declined about 1 percent immediately after 1 p.m., when a letter from FBI Director James B. Comey to lawmakers detailing the continuing investigation became public. Comey had previously said that the FBI had completed its investigation.

Prices in the Nasdaq Composite index gave up 0.9 percent, while the Dow Jones industrial average declined 0.8 percent.

Analysts and experts noted several reasons that markets might have sold off on the news. One argument is that investors think markets would do better under Clinton as president than under her Republican rival, Donald Trump.

Trump has said he would deport large numbers of illegal immigrants, increasing the cost of labor in the United States, and that he would impose tariffs on Mexican imports. Both policies could result in steeper prices for goods and services in this country.

Traders unloaded Mexican pesos after the news, driving the price of the currency in dollars down 2 percent, from 5.3 cents per peso to 5.2 cents. Many traders are concerned that if Trump is elected and imposes tariffs on Mexico, Americans will purchase fewer Mexican imports and the demand for pesos with which to buy Mexican goods will decline.

Trade with the United States is crucial to Mexico's economy. About 73 percent of Mexican exports are sold to the United States, according to Bloomberg News.

Whether they would be beneficial or detrimental, however, the effects of Trump's policies on the economy would be difficult to predict — a second source of anxiety for traders. On the trail, Trump himself has wavered in his stance on economic issues, and it is unclear how much of his agenda Congress would permit him to implement.

“Clinton does represent the status quo. Trump represents change, and it’s unclear what the change is,” said Mark Zandi, the chief economist at the private research firm Moody's Analytics, who has predicted grave economic effects if Trump's proposals were implemented. “That just makes investors very nervous.”

The Volatility Index of the Chicago Board Options Exchange, which represents investors' expectations of future uncertainty, skyrocketed 18 percent following the news from Washington.

The abrupt increase in volatility was especially notable, as the index has remained near historic lows for most the past year.

“Why are markets so nervous about Trump yet so calm overall?” Eric Zitzewitz, an economist at Dartmouth University, asked. “We're puzzled by that.”

The price of gold climbed to $1,284 per troy ounce, an increase of about 1.1 percent, while the price of Treasury bonds increased modestly — additional indicators that investors were looking for safe bets.

“This is a small glimpse into what the bond market thinks is going to happen if Trump is elected,” Bloomberg News quoted Thomas Roth, senior Treasury trader at MUFG Securities Americas Inc., as saying. “The market has made it clear that they think a Trump victory would be bad for stocks and would create more uncertainty in the economy.”

Investors rallied as the close of the trading day approached, and prices recovered modestly. By 2 p.m. the Dow Jones industrial average had made up the day's losses, although the other major equity indexes closed in the red.