California and federal officials had strong indications of oil in the water off the coast of Huntington Beach on Friday evening, records reviewed by The Times show, more than 10 hours before the operator of an oil platform reported it to authorities.

The documents raise questions about how the massive leak was handled in its first hours and why authorities did not alert the public and elected officials sooner. Residents have complained about the time it took to alert the public about the scope of the catastrophe and initial claims by government agencies that oil would not reach land.

“We need to get to the ground truth as to when it was reported, to whom it was reported and why if ... governmental agencies knew there was a spill Friday night or even Saturday morning, they failed to notify those of us who have a responsibility [to the public],” said state Sen. Tom Umberg, who represents a district where beaches have been hit by oil.

The Office of Spill Prevention and Response, a division of the California Department of Fish and Wildlife charged with handling such emergencies, said in a report obtained by The Times that it was first notified of an “observed sheen in federal waters several miles off the coast of Huntington Beach” on Friday at 10:22 p.m., though the source and volume were unknown.

That report was based on information provided to California authorities by the National Reporting Center, the designated point of contact for all oil and chemical discharges into the environment, which took a report about a possible spill earlier Friday night, according to documents reviewed by The Times.

Records show that the National Reporting Center informed the state’s Office of Emergency Services that a ship on Friday evening had reported a possible oil slick 4.5 nautical miles west of Huntington Beach.

Satellite imagery, used to take a closer look about 45 minutes after that report, measured the area of the spill at 2.8 by 0.7 nautical miles. While the satellite images could not definitively identify the substance as oil, the report said the overhead imagery allowed for “high confidence” that it was petroleum. The report also said the spill extended beyond the borders of the image and could be larger.

Shortly thereafter, federal and state authorities began to mobilize, forming a command center to handle the emerging crisis. But darkness likely prevented them from examining the slick up close. Nancy Kinner of the Center for Spills and Environmental Hazards at the University of New Hampshire said it is difficult and uncommon for authorities to work on spills at night.

By early morning Saturday, more reports were coming in, according to the records reviewed by The Times, including one from the company that owns the oil platform.

Brian Ferguson, spokesman for the Office of Emergency Services, which acts as the receiver for spill reports for the state, said his agency was notified by Amplify Energy — the company that owns the aging infrastructure — at 8:55 a.m. Saturday that a pipeline leak had occurred at about 2:30 a.m.

Martyn Willsher, Amplify’s chief executive, said in a Monday press conference that the company did not know about the leak until Saturday. He said Amplify was unaware on Friday of reports from Orange County residents who had been smelling fuel that day.

“We ... noticed the sheen, immediately contacted the platforms, and the platforms instantaneously started the incident plan,” Willsher said.

The U.S. Coast Guard is investigating whether the oil company failed to notice a drop of pressure in the pipeline, resulting in a delayed response that allowed oil to flow for hours unfettered, a high-ranking federal official told The Times on Monday. That investigation is being handled as a potential negligence issue by Coast Guard criminal investigators, who operate separately from officials involved in the cleanup, said the federal official, who was not authorized to speak publicly about the inquiry.

Richard Charter, a senior fellow at the nonprofit Ocean Foundation who has worked on issues related to offshore oil for 40 years, explained that whenever the pressure in a pipeline drops, indicating a possible leak or failure in the system, an alarm is supposed to be triggered.

“You don’t have pressure drop in a pipeline and not know about it. And that raises the question: Why did the response kick in a day late?” said Charter, who added that federal regulators should be making sure the alarms and emergency protocols are up to date. “Somebody did nothing. ... You shouldn’t have to wait until the oil’s lapping up onto the shoreline to find out that you’ve had an oil spill. That’s ridiculous.”

Other witnesses on Saturday morning also reported the sheen. Dylan Bartell, 17, who was out with his father on their fishing boat, said he was below deck around 9 a.m. when his father called him up to see oil surrounding the boat, the Babe Del Mar. Visibility was bad, but they were about nine miles offshore, heading toward Catalina.

“We could see that it went on for miles, and there was just thick oil beneath us,” Bartell said.

He and his father radioed the Coast Guard but did not receive an immediate response, so the teenager looked up how to report an oil spill and called it in to authorities. Later, a second radio attempt to the Coast Guard received a response, with authorities telling Bartell they had received other reports, he said. Bartell’s report was forwarded to Cal OES Saturday at 9:17 a.m.

Elected officials were not notified of the spill until Saturday afternoon, according to an email obtained by The Times and interviews with state legislators.

Assemblywoman Janet Nguyen, whose district has beaches that have been hit with oil, said she did not receive word until a public tweet from the Coast Guard on Saturday afternoon. Also Saturday afternoon, a Coast Guard official told The Times: “We were alerted quickly. We really believe we will keep this to a small contained incident.”

But by Saturday night, oil was hitting the coast and polluting environmentally sensitive wetlands, as well as beaches. On Monday, the plume was moving south, toward Laguna Beach.

“Quite frankly, these kinds of incidents should have been made known to us before they were made public, because our constituents will have questions,” Nguyen said.

California agency leaders held a briefing on Monday night with elected officials. Sources who participated said officials continued to assert that they did not know about the leak until Saturday, when it was publicly announced.