* TSX ends down 55.06 points at 13,619.19
* Materials, energy, financials all weaker
* Cameco tumbles 13 pct, Uranium One sinks 28 percent
* Insurers drag on financials, Manulife off 3.5 percent (Updates to close, adds details, commentary)
By Claire Sibonney
TORONTO, March 14 (Reuters) - Toronto's main stock index ended modestly lower on Monday, led down by weaker energy producers, insurers and miners on worries about the impact of the devastating earthquake and tsunami in Japan.
Japanese engineers raced to prevent a meltdown at a stricken nuclear plant, as rescuers scrambled to help millions left without food, water or heating in the wake of the disaster. [ID:nLDE72D2FT]
Shares of Cameco Corp (CCO.TO), the world's second largest uranium miner, plunged 13 percent to C$31.70. Uranium One UUU.TO sank 28 percent to C$4.31 and Paladin Energy (PDN.AX) sold off 21 percent to C$3.67. [ID:nN14135943]
"This does cause some potential buyers to question ... the safety of nuclear as part of the overall energy cocktail," said Paul Taylor, chief investment officer at BMO Harris Investment Management.
"Obviously we do not know the extent to which the issues in Japan will accelerate, but certainly this doesn't bode well for the demand for nuclear."
Energy and base-metal shares slipped 0.2 percent and 2 percent respectively, despite stabilizing commodity prices. [O/R] [MET/L]
Suncor Energy (SU.TO) fell 0.5 percent to C$42.09 and Teck Resources TCKb.TO -- under additional pressure after it trimmed its first-quarter coal sales forecast -- tumbled 2.7 percent to C$49.56. [ID:nN14132991]
"The market has to price in multiple exogenous shocks," said Stephen Wood, chief investment strategist for Russell Investments in New York, referring to the geopolitical turmoil in North Africa and the Middle East and the broader market pullback prior to the devastating tsunami and earthquake in Japan.
"Everybody who is human is just standing in awe of the human tragedy ... I think that's probably the first response."
Wood said the short-term impact would likely remain negative, but in the longer term, the rebuilding effort could be stimulative for overall demand in Japan.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE ended down 55.06 points, or 0.4 percent, at 13,619.19. Seven of the 10 main sectors were lower.
Financials were flat but insurers were hit by some of their reinsurance exposure in Japan, as well as weaker equity markets in general, said Taylor. Manulife Financial (MFC.TO) fell 3.5 percent to C$16.74, while Sun Life Financial (SLF.TO) was down 0.5 percent at C$30.16. [ID:nN14193961]
"Most people felt the that the S&P/TSX was overbought and this is a healthy chance for reflection after the very strong economic data, very strong earnings data," added Taylor.
"Throw in a natural disaster and some significant geopolitical tension and you have the backdrop for a bit of a market setback until we decide what the next move upward is."
($1=$0.97 Canadian) (Reporting by Claire Sibonney; editing by Rob Wilson)