Concerns that a global glut of supplies will continue to grow prompted another drop in oil futures on Monday to their lowest settlement since early April. The move lower led one analyst to warn that the market may soon experience a “vicious sell off.”

Still, U.S. prices managed to hold above $50 a barrel in the wake of a weekly decline in the number of active U.S. rigs drilling for oil. West Texas Intermediate August crude fell 74 cents, or 1.5% to settle at $50.15 a barrel on the New York Mercantile Exchange. That was the lowest settlement for a most-active contract since April 2. The August contract expires Tuesday.

September Brent crude ended at $56.65, down 45 cents, or 0.8%, on the ICE Futures exchange. “Technically-minded market participants may have noticed that WTI’s attempts to recover at various stages last week proved futile,” said Fawad Razaqzada, technical analyst at FOREX.com. Prices weren’t able to break above the $54 resistance level, he said. “The lack of any noticeable buying interest following the huge price slide from earlier in the month suggests that the bears are in full control and that the selling may have further momentum left behind it,” he said in a note. “We could see a vicious selloff in oil over the coming days.”

Oil prices have been hit by a stronger U.S. dollar, the likely return of Iran to the oil market by year’s end and strong crude supplies from Organization of the Petroleum Exporting Countries, said Rob Haworth, senior investment strategist at U.S. Bank Wealth Management. “Solid” U.S. production data and softer global growth and likely soft global energy-demand growth are also contributing to price pressures, he said. For now, the $50 level is a key support level for WTI oil on the downside, analysts said. WTI prices briefly fell below $50 Monday to trade as low as $49.85 a barrel. If the oil bulls “manage to defend the $50 handle successfully, then we may, after all, witness some price recovery,” said Razaqzada.

Offering some support to prices, Baker Hughes on Friday reported that the U.S. oil-rig count fell after rising over the previous two weeks. It was down by 7 to 638 as of July 17.