A world-wide oil glut and uncertainty over economic growth combined to send oil futures sliding Monday, with the global crude benchmark trading below $50 a barrel for the first time since January.

Brent crude on London’s ICE Futures exchange dropped $2.69, or 5.2%, to close at $49.52 a barrel, the lowest finish since Jan. 29. The U.S. benchmark, West Texas Intermediate crude, also plunged. WTI crude for delivery in September dropped $1.95, or 4.1%, to end at $45.17 a barrel, the lowest level for a most-active contract since March 19.

Oil slumped amid a confluence of negative factors, though there appeared to be no individual catalyst for the leg lower, said Robert Yawger, director of energy futures at Mizuho Securities. Oil was vulnerable to further pressure after last week’s downbeat assessment of market prospects by Exxon Mobil and Chevron and a rise in the U.S. oil-rig count. Add in weak economic data from China over the weekend and talk by Iran’s energy minister over the country’s ability to quickly ramp up production and crude was prone to further weakness, Yawger said. The slide gained momentum as oil took out key technical levels, inspiring stop-related selling. Investors “are still feeling the hangover of last week’s less than impressive macro data as both crude-oil benchmarks display a continuation of the recent bearish price moves,” said Kash Kamal, senior research analyst at Sucden Financial, in a note.

Remarks over the weekend by Iran’s oil minister, who said the country could boost output within a week of the lifting of international sanctions, also added to the bearish tone. Speaking in an interview with Iranian state television, Oil Minister Bijan Namdar Zangeneh said the country could lift production by 500,000 barrels a day within a week of the lifting of sanctions and by one million barrels a day within a month after that, according to Bloomberg. “With the second-largest barrel-per-day output in OPEC before the sanctions were enforced, Iran has a lot of market share to recover and officials have made it clear that any refusal from other OPEC members to accommodate this lost share in export markets would ultimately result in lower crude prices,” Kamal said. Meanwhile, the oil-rig count in the U.S. rose by five to 664 last week, Baker Hughes Inc. reported Friday, undercutting expectations that the country’s oil production had peaked.

In China, the Caixin manufacturing purchasing managers index, a gauge of nationwide manufacturing activity, fell to a two-year low of 47.8 in July, compared with 49.4 in June. Though Chinese oil imports have held steady despite a stream of negative economic data from the country, any sign of weakness in China’s demand has been enough to drive the market further into a bearish mode.

Demand is currently near seasonal peak levels and will fall in the second half of the year, Morgan Stanley said in a report. The firm said supply pressures could increase in 2016 as sanctions on Iran might be lifted. “That said, prices are likely near the bottom of the range and retesting year-to-date lows is unlikely,” the report said. “Healthy transport demand, [capital expenditure] cuts, low spare capacity and investor appetite should limit the downside.” U.S. production growth should slow as unconventional shale production is expected to be the quickest to respond to low oil prices compared with larger and more-complex international projects, which require more lead time, according to the report. Also, crude-oil production from the Organization of the Petroleum Exporting Countries should continue to grow by 800,000 barrels a day because of capacity additions in Iraq and Angola, as well as higher output from Saudi Arabia.