(CNN) Oil pipeline company officials said Wednesday that as many as 105,000 gallons of crude oil may have spilled from a ruptured pipeline on the California coast.

The 24-inch pipeline ruptured along the Santa Barbara coast, leaking the oil near Refugio State Beach , a protected state park, just before Memorial Day weekend marks the start of the summer tourist season.

Houston-based Plains All American Pipeline based the estimate -- what it called a worst-case scenario -- on the typical flow rate of oil and the elevation of the pipeline, said Rick McMichael, the company's director of pipeline operations.

The pipeline is still underground, so it will take a few days to determine how much crude oil was actually spilled.

McMichael told reporters an estimated 21,000 gallons of crude had gone into the Pacific Ocean.

The cause of the spill was still being investigated, he said, but there were problems Tuesday morning at two of the company's pump stations.

Plains Chairman Greg Armstrong said he was deeply sorry for the spill.

"We apologize for the damage that has been done to the wildlife and to the environment, and we're very sorry for the disruption and inconvenience that it has caused the citizens and visitors of this area," he said.

Armstrong said his company had been given permission to work through the night on the cleanup.

"This spill is unlike ones that we've responded to in the past." said Coast Guard Capt. Jennifer Williams at an earlier news conference. The spill originated inland, where the U.S. Environmental Protection Agency has jurisdiction, but has gone to the shoreline and the water, where the Coast Guard has responsibility -- thus the need for a combined response.

"Oil recovery tends to be a complicated process that involves a lot of manual labor," Williams said. "It can be a slow process, but we want to make sure that we do it right so we can get the beaches back to their pristine condition."

EPA emergency response coordinator Michelle Rogow asked that people refrain from working on their own to clean up the beach. "We request (you) give us the space to be able to assess and clean up this spill with the proper tools, equipment, personnel and resources that are needed," she said.

Health officials said that no one has needed medical care because of the spill.

Refugio State Beach

A thick, black, greasy, 9-square-mile oil slick now snakes along what was the pristine coastline of Refugio State Beach, Williams said Wednesday evening.

"It will continue to disperse over time and spread out due to the winds and currents," she said.

JUST WATCHED Burst pipeline cloaks California beaches with oil Replay More Videos ... MUST WATCH Burst pipeline cloaks California beaches with oil 01:11

, the Reagan Ranch, 20 miles west of Santa Barbara. It's a popular camping destination, treasured by visitors because it is on a raw, unspoiled stretch of coast. It is gorgeous and remote -- not a place with a lot of commercial stores and T-shirt shops. Palm trees line the shore. Crystal blue water laps the white, sandy beach -- all framed by verdant green hills. Refugio State Beach sits below Rancho del Cielo , the Reagan Ranch, 20 miles west of Santa Barbara. It's a popular camping destination, treasured by visitors because it is on a raw, unspoiled stretch of coast. It is gorgeous and remote -- not a place with a lot of commercial stores and T-shirt shops. Palm trees line the shore. Crystal blue water laps the white, sandy beach -- all framed by verdant green hills.

It's also an extremely popular campground. Several thousand people visit over the Memorial Day weekend. A note on the California Department of Parks and Recreation website says the beach is "closed indefinitely" due to the oil spill.

The environment

Of course, a big concern is the environment. There are shorebirds that live in the area -- the snowy plover and least tern nest on sandy beaches, and the cormorant can dive deep to find food. Officials want to make sure that none of the birds or other wildlife suffer damage from the spill.

"An aggressive and effective cleanup response to the spill is underway," said Mark Crossland with the California Department of Fish and Wildlife. "It will go on as long as necessary.

"Every effort will be made to minimize the damage to the environment, including taking care of oiled wildlife," said Crossland.

Fishing and shellfish harvesting have been closed in Santa Barbara County until further notice.

There's also concern about the next park down the road, El Capitan State Beach , with sandy shores and rocky tide pools. Thousands of people are expected to flock to El Capitan over the Memorial Day weekend. It's located on another unspoiled stretch of coast. Visitors go there to kayak, hike and picnic.

The response

The California Department of Fish and Wildlife has three 65-foot vessels on the scene, collecting oil, and six boom vessels in operation, according to its Twitter feed. There are 73 people in the field collecting oil and protecting the shorebirds.

"We are monitoring, the Coast Guard is on the scene and federal and state agencies and the operator have established an Incident Command/Unified Command," a White House official said. Also, two inspectors with the Pipeline and Hazardous Materials Safety Administration are at the site of the spill, and "additional inspectors are scheduled to arrive today."

"It's still too early for numbers on the amount of oil," said Brad Alexander, a spokesman for the California Office of Emergency Services.

"I can tell you we have more than 100 people responding in the EOC (Emergency Operations Center) right now. They have several ships, scooping up oil and assessing the boundaries on the water," he said.

The cleanup

"We continue to see it's not a question of if there is going to be an oil spill but when?" said Maggie Hall from the scene of the spill. She is an attorney with the Environmental Defense Center. "It's a constant threat. And as you can see the cleanup is not easy."

It is painstaking work, evidenced by several dozen workers in white protective suits and helmets on the beach raking together balls of tar from the shore, sand and rocks and putting them into plastic bags.

The Coast Guard has seven ships in the area, laying down protective booms, skimming the water and collecting the oil to prevent it from spreading.

Plains All American Pipeline said it found the spill affected its Las Flores-to-Gaviota pipeline, which was built in 1987. It said the leaked oil reached a culvert, and it spilled into the Pacific Ocean from there. The culvert was later blocked to stop the flow.

Armstrong said the pipeline had been recently inspected.

#Update CG overflight photo from Refugio State Beach oil spill pic.twitter.com/MCxtce8xvN — USCGLosAngeles (@USCGLosAngeles) May 20, 2015