Oil prices hovered near 13-month highs on Tuesday on the back of a cold snap shutting wells in Texas, the biggest crude producing state in the United States, while a wage deal in Norway averted outages in Europe, capping gains.

Prices also gained after Yemen’s Houthi group attacks on Saudi Arabia, raising supply concerns in the world’s biggest oil exporter, while vaccine-driven optimism over a global economic recovery from the COVID-19 pandemic also supported.

US West Texas Intermediate (WTI) crude futures gained 41 cents, or 0.7 percent, to $69.88 a barrel by 0836 GMT, after touching their highest since early January 2020.

The cold weather in the US halted Texas oil wells and refineries on Monday and forced restrictions on natural gas and crude pipeline operators, leaving about 4 million homes and businesses without power.

Texas produces roughly 4.6 million barrels of oil per day and is home to 31 refineries, the most of any US state, according to Energy Information Administration data, including some of the country’s largest.