A fire that engulfed a fuel pump at Boston Logan International Airport Tuesday afternoon forced the cancellation or delay of about 15 percent of the flights out of the airport, and may lead to more delays on Wednesday, a Massport official said.

Fire investigators have not determined the cause of the fire, which sprung up around 5 p.m. in one of the airport’s 12 fuel pumps, but the blaze does not appear to be suspicious, said Edward C. Freni, the airport’s director of aviation. No injuries were reported.

Firefighters had the fire under control within a half-hour, Freni said. But the underground system that transports fuel to the planes remains off while engineers assess the damage.

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“This is very unusual, it’s catastrophic as far as airport operations are concerned,” Freni said at an evening press conference at Logan.

Citing security concerns, Freni would not discuss the threat the fire posed to sensitive facilities such as the large tanks that store fuel and are located close to the fire scene.

Once Massport notified airlines of the problem, most domestic flights bound for Logan were able to take on extra fuel before departing, enabling them to land in Boston and take off again without refueling, Freni said.

But several flights, including many international arrivals, were forced to divert to other New England airports to refuel before carrying on to Logan.

Freni said engineers had not yet determined the cost of the damage or how long the fueling system will remain shut down, but he tentatively predicted that operations would return to normal Wednesday.

“We recommend that anyone with travel plans tonight or tomorrow contact their airlines,” he said. “We do feel that there will be some impact tomorrow.”