Company spokesman Steve Rinehart said the leak did not affect overall production and is unrelated to the power outage that temporarily shut down Prudhoe Bay on Friday.
Rinehart said the leak happened late Monday. The well had been shut down since January for routine maintenance, he said.
"A worker was bringing a well back online, and just as he was doing it, he discovered a leak in the well line," Rinehart said. "He was right there when it happened, so within minutes, he shut in the well."
Two officials from separate state departments say the company notified the state and shut the well down immediately. Work is under way to clean up the leak.
Even as the spill was deemed minimal, Department of Environmental Conservation spokeswoman Lynda Giguere said an investigation still is under way.
She said there was no immediate word on how much oil was leaked, but it was a matter of gallons rather than barrels. There are 42 gallons in a barrel.
Allison Iversen, coordinator for the state's Petroleum Systems Integrity Office, said the oil leaked for about five minutes.
The entire field temporarily shut down on Friday when a vehicle clearing snow drifts damaged the power supply to processing centers.
The vehicle struck a compressed air line at the central power station. That line controls the power station's fuel system. As a result, seven plants shut down.
Rinehart said BP has dealt with some minor maintenance issues while ramping up again. That kept the company from full production, or about 380,000 barrels of oil daily, at Prudhoe Bay.
Full production wasn't expected to resume for several days.
LOOKING BACK: Read past coverage on the Prudhoe Bay oil spill at
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