U.S. energy firms this week added oil and natural gas rigs for the first time in three weeks as relatively high crude prices encouraged some firms to drill more, mainly in the Permian Basin.

The oil and gas rig count, an early indicator of future output, rose four to 763 in the week to Sept. 16, its highest since August, energy services firm Baker Hughes Co. said in its closely followed report.

Baker Hughes said that puts the total rig count up 251, or 49%, over this time last year.

U.S. oil rigs rose eight to 599 this week, while gas rigs fell four to 162.

The biggest increase in rigs was in the Permian Basin in Texas and New Mexico, the biggest U.S. oil field, which rose by three to 343 this week, the most since August.

After rising for a record 24 months in a row, the combined rig count fell in August and was on track to fall again in September due to supply chain issues, infrastructure constraints and inflation, according to energy executives.

While oil output in the Permian is due to rise to a record high in October, all of the other regions are still below their peaks—owing to higher costs and less advantageous locations.

Morgan Stanley this week noted that U.S. oil output is up about 520,000 bbl/d in the first half of the year, which puts it on track to fall short of its estimate for growth of 800,000 bbl/d—it now expects production to rise by 650,000 as it points to slowed growth in rig counts.