Toronto stocks closed lower Monday as investors mulled over the possibility of further terror attacks following the bombings in Spain, and turmoil in the executive suite at Nortel Networks weighed on the market.

The S&P/TSX composite index fell 157.63 points, or 1.83%, to close at 8,434.41. Volume was heavy with 313 million shares changing hands.

The technology sector slumped 6.25% to lead the market lower after Nortel said it had put its CFO and controller on paid leaves of absence pending a review. Last week, the company said it may restate its 2003 results for the second time in six months.

Nortel sank $1.60 to $6.98. Other technology shares also saw big declines. Hummingbird fell $1.84 to $30.46.

The pain was shared across the TSX with declines of more than more than 1% in the telecoms, health-care, and consumer discretionary groups.

The materials group fell 2.32% as mining stocks fell 3.57% amid concerns that there is little to drive demand for base metals.

Inco fell $2.04 to $44.64 while Falconbridge shed $1.30 to $33.45.

Among the day’s few winners, Canadian National Railway shares rose 31¢ to $51.40. Union workers will vote this week on a new contract deal that could end a nearly four-week strike at the country’s biggest railway.

The junior S&P/TSX Venture composite index slid 22.62 points, or 1.21%, to 1,839.99.

On Wall Street, stocks fell sharply as investors fled the market on signs that al Qaeda may have been behind the bombings in Spain.

The blue-chip Dow Jones industrial average ended down 137.19 points, or 1.34%, at 10,102.89, its lowest close since mid-December. The broader S&P 500 fell 16.08 points, or 1.43%, at 1,104.49. The tech-heavy Nasdaq composite index dropped 45.53 points, or 2.29%, to 1,939.20.