Toronto's main stock index was dragged lower Wednesday amid fears that the global oil supply glut is growing, not shrinking.

The S&P/TSX composite index fell 92.42 points to 15,372.14, with the majority of the weakness coming from energy and telecom stocks.

A report by the U.S. Energy Information Administration showed an unexpected buildup in crude oil inventories of 3.3 million barrels last week. Experts had expected stockpiles to decline by 3.5 million barrels.

Oil futures plunged on the news, as the July crude contract sunk $2.47 at US$45.72 per barrel -- its lowest price in more than a month.

"The industry itself has to take a look in the mirror and see that they're causing a lot of the problems themselves," said Michael Currie, vice president and senior investment adviser at TD Wealth.

"We just saw the 20th straight week of U.S. rig counts go up. If you're out there trying to protect the price of your commodity, why do you keep pumping more and more?"

In New York, stock markets finished moderately higher as investors looked ahead to a busy Thursday filled with a number of events that could prove negative for indices.

Among them include the testimony by former FBI director James Comey in front of a congressional hearing about his abrupt ouster on May 9 by U.S. President Donald Trump and the investigation into alleged U.S. election meddling by the Russians.

Comey will testify that Trump sought his "loyalty" and asked what could be done to "lift the cloud" of investigation shadowing the White House, according to prepared remarks released ahead of his appearance on Capitol Hill.

Overseas, Britons will also head to the voting booths for what is anticipated to be tight race, and the European Central Bank is slated to meet to discuss monetary policy.

On Wall Street, the Dow Jones industrial average gained 37.46 points to 21,173.69, the S&P 500 index added 3.81 points to 2,433.14, and the Nasdaq composite index was up 22.32 points to 6,297.38.

In currencies, the Canadian dollar dipped 0.17 of a U.S. cent to an average price of 74.12 cents US.

Elsewhere in commodities, the July natural gas contract was down two cents at US$3.02 per mmBTU, the August gold contract retreated $4.30 to US$1,293.20 an ounce and the July copper contract remained unchanged at US$2.55 a pound.

-- With files from The Associated Press.