The crash of a U.S. Marine Corps F-35B that temporarily grounded the entire fleet of next-generation jets in 2018 was caused by a manufacturing defect in a fuel tube made by a United Technologies subcontractor, according to congressional investigators.

The defect “caused an engine fuel tube to rupture during flight, resulting in a loss of power to the engine,” the Government Accounting Office said this week in a report on major weapons systems that referred to the September crash in South Carolina. The Pentagon told the watchdog that it identified 117 aircraft — about 40 percent of the worldwide F-35 fleet at the time — with the same type of fuel tubes that had to be replaced.

The disclosure was the first official information about the crash since the Pentagon program office in late October issued a status statement while the Marine Corps was still conducting its investigation. United Technologies Corp.’s Pratt & Whitney unit “is fully responsible” for “the propulsion system and has the lead in working” the failure analyses, according to the statement at the time.

A spokeswoman for the Pentagon F-35 program office deferred comment to Pratt & Whitney, whose spokesman, John Thomas, said the company had no comment.

Marine Corps spokesman Captain Chris Harrison said in a statement that the crash probe is continuing, and that the results will be released once complete. The Corps has replaced all of the relevant fuel supply tubes and “we continue to strive each and every day to ensure the safety and readiness of our aircraft,” he added.

The Sept. 28 crash of the F-35B near Beaufort, South Carolina, was the first in the two-decade old program’s often-rocky history of delays, cost increases and technical glitches. Although the pilot safely ejected, the incident prompted concerns about the aircraft, which is being built by and sold to an international consortium of U.S. allies, including the U.K, Italy, Australia and Turkey.

The Pentagon program office last year said “more than 1,500 suppliers are on the F-35 program and this is an isolated incident which is quickly being addressed and fixed. Safety is our primary goal.”

The defective part identified in the report provides operating pressure to the engine and fuel to the engine combustor.

Aside from the defect, Pratt & Whitney’s recent track record delivering engines on time has been spotty. Deliveries surged to 81 in 2018 from 48 in 2012, according to the GAO — yet 86 percent of those were delivered late, up from 48 percent in late 2017. The delays were due in part to an increase in the “average number of quality issues per engine” — 941 in 2018 against 777 a year earlier, the GAO said.

Pratt & Whitney told the GAO that “its late engine deliveries increased in 2018 partially due to a subcontractor that did not have all of the needed tooling in place to produce more F-35B engines,” according to the report.

The F-35 is the Pentagon’s most expensive weapons program, at a projected cost of more than $428 billion. More recently, a Japanese F-35A crashed off Japan’s coast in April, with only portions of the jet’s wreckage found since then despite a monthlong search. The cause of the crash is under investigation. The jet’s pilot hasn’t been found.