Speaking at the Tuesday afternoon press conference, the official said about 30 tons of rock per hour are being placed representing about 40 truckloads an hour. Also, two helicopters continue to drop rocks every couple of minutes.
A total of three counties, Butte, Sutter and Yuba, had communities under the evacuation order. Oroville, located in Butte County, is about 70 miles north of Sacramento.
Even with the evacuation lifted, a major storm system is forecast to reach the region within 48 hours and could produce significant precipitation for Northern California and the Oroville area. The storm had been expected to reach Oroville late Wednesday but now forecasters say it will likely be Thursday and stick around through next week.
Residents faced traffic problems after the evacuation order went out and authorities said they are preparing to handle thousands of people returning. There were hints the evacuation would be lifted when people spotted road blocks being removed just after noon Tuesday.
Some of the evacuees have been staying at about a dozen shelters established in the region, including the fairgrounds in Chico, while others fled to hotels in locations such as Sacramento.
There have been concerns about Oroville Dam safety since the erosion of the primary spillway was discovered a week ago. Officials have insisted the dam itself is not at risk.
Last week, claims surfaced that state and federal officials failed to heed safety warnings about Oroville more than a decade ago. The Oroville Dam — the nation's largest earthen dam — was completed in the late 1960s when Ronald Reagan was governor of California.
On Monday, the Federal Energy Regulatory Commission ordered the the state water agency "to initiate immediate design of emergency repair to minimize further degradation of both the emergency spillway and the service spillway."
Croyle, the acting director of DWR, defended the dam's emergency spillway design saying it was "built to the standards at the time [in the 1960s]. We are reviewing that information now."
Speaking late Monday, Gov. Jerry Brown too defended the state's handling of the dam spillway crisis and welcomed more scrutiny.
Meantime, Brown late Monday requested federal assistance from President Donald Trump for the Oroville Dam incident. That request is still pending approval from the president.
Even so, during a press briefing Tuesday, White House Press Secretary Sean Spicer said the president was "keeping a close eye" on the dam situation in California.
While Spicer didn't say whether Trump would grant an emergency declaration, the presidential spokesman said "we will be working alongside with FEMA and appropriate government entities to make sure that we are doing everything we can to attend to this matter."