A pepper spray incident in downtown Washington sent a scare through Wall Street today, triggering temporary stock plunges that dropped the Dow Jones industrial average by 60 points in a matter of minutes.

The Dow and other indexes quickly bounced back but never fully recovered.

The Dow, which was trading slightly higher before the incident, closed off 5 points at 10,168.83.

The Standard & Poor's 500 stock index gained less than 2 points to 1,105.93.

The Nasdaq Stock Market composite index, up 25 points in morning trading, closed up 12 at 1,850.93.

The plunge reflected not only how skittish Wall Street is, but also how volatile the market can become when the trading is as thin as it has been recently. Friday and Monday were the two slowest days of the year for the Dow, but frantic buying and selling set off by the pepper spray incident brought today's volume back closer to normal.

Initial reports flashed to Wall Street suggested "mass casualties" resulted from the incident in the International Square building that runs through the block from K Street to I Street along 19th St. N.W. With security tight at the nearby World Bank and International Monetary Fund buildings, almost two dozen emergency vehicles scrambled for what turned out to have been caused by teenagers accidentally.

The crude oil market also had a wild day, with the price of futures climbing $1.88 a barrel to $44 a barrel on the New York Mercantile Exchange. The jump in prices came after Energy Department reports showed U.S. stockpiles fell by 4.2 million barrels last week -- roughly 10 times as much as oil traders were expecting.

Today was a weak start for what is traditionally a bad month on Wall Street. The Stock Traders Almanac ranks September as the worst losing month of the year for all three of the most closely watched indexes.

Typically the month starts out okay, according to Wall Street's answer to the Old Farmers' Almanac, but it ends significantly lower as investors come back after Labor Day and clean out their portfolios.