OKLAHOMA CITY (AP) — Collections to Oklahoma's main government operating fund are continuing to outpace the estimate, but state finance officials are cautioning that lower oil prices are expected to start driving some of those collections down.

The Office of Management and Enterprise Services reported Tuesday that December collections to the General Revenue Fund totaled $620 million, nearly 9 percent above the monthly estimate.

For the first six months of the fiscal year, collections have exceeded the official estimate by nearly 5 percent.

But Oklahoma's new chief operating officer, former Son...