Stocks remained sharply lower by mid-afternoon Tuesday as crude oil closed at its lowest level since June 27. 

The S&P 500 was down 0.9%, the Dow Jones Industrial Average fell 0.78%, or 140 points, and the Nasdaq declined 1.1%.

Uncertainty over the timeline and execution of the United Kingdom's exit from the European Union left markets rattled on Tuesday. The U.K.'s central bank also sounded a dovish call, unnerving investors already unsure about the global effect of a Brexit.

Crude oil was in retreat after closing last week with a five-day gain of 2.8%. The commodity ended the second quarter on Thursday with gains of 26%, its best quarterly performance since 2009, thanks to disruptions to global oil production, particularly in Canada, Nigeria and Venezuela.

The commodity was also under pressure as Nigerian production rebounded in June, pushing total output from the Organization of Petroleum Exporting Countries to its highest level since January. A Bloomberg survey showed OPEC production increasing by 240,000 barrels a day in June. 

"The increase in OPEC production threatens to postpone the anticipated rebalancing of the global market," said Timothy Evans, energy futures analyst at Citi. 

West Texas Intermediate crude oil dropped 4.9% to $46.60 a barrel.

The energy sector was the worst performer on markets on Tuesday. Major oilers including Exxon Mobil (XOM - Get Report) , PetroChina (PTR - Get Report) , Total (TOT - Get Report)  and Royal Dutch Shell (RDS.A - Get Report) were falling. The Energy Select Sector SPDR ETF (XLE - Get Report) slid 2.5%. 

The Bank of England said Tuesday it would reduce the amount of capital banks need to hold to free up more money for lending to businesses and households following the aftermath of Great Britain's vote to leave the European Union. Bank of England Gov. Mark Carney said that the central bank has the scope to deal with Article 50, which will kick off Britain's exit, when it is invoked.

"The Bank of England is making strenuous efforts to reassure the markets that it can provide ample liquidity and relax monetary policy to counter some of the effects of the Brexit uncertainty shock on the economy," Societe Generale analysts wrote in a note.

Stocks had rallied in the previous week, wiping out much of the Brexit selloff, thanks to a spike in speculation that the turmoil in Europe will delay a rate hike in the U.S. and increase the chances of monetary stimulus from global central banks. The protracted time for an exit from the EU -- likely at least two years -- also gave investors a reason to buy back in the near term.

U.S. factory orders in May declined at a faster pace than expected. Orders declined 1%, according to the Census Bureau, a wider decline than an expected 0.8%. Orders have slowed since a 1.8% increase in April.

Harley-Davidson (HOG - Get Report) slid 11%, giving back much of the gains achieved on Friday. Shares had surged on speculation of a possible takeover deal from private-equity firm KKR in the pipeline.

Delta (DAL - Get Report) cut its profit margin forecasts for its June quarter. The airline pointed to a 5% decline in passenger revenue in June and the higher cost of fuel as reason for the weaker-than-expected quarter.

Tesla (TSLA - Get Report) fell 1.7% after releasing a second-quarter sales update that fell well short of company estimates. The electric car company said it produced 18,345 vehicles in the second quarter of 2016, a 20% increase from the previous quarter. However, a late-quarter production increase meant deliveries reached only 14,370 vehicles, below an expected 17,000.

Walt Disney's (DIS - Get Report) Finding Dory topped the weekend box office for the third week in a row, generating an estimated $50.2 million in North American ticket sales over the four-day holiday weekend. The animated sequel has taken in $538.3 million globally during its three-week run. Warner Bros.' The Legend of Tarzan pulled in $38.1 million domestically in its weekend debut, a disappointing haul and just a fraction of its $180 million production cost.