Hawaii’s congressional delegation is asking the U.S. Department of Defense’s Inspector General to investigate whether the Navy “covered up evidence or intentionally delayed” notification to Hawaii regulators earlier this year about a pipeline leak into Pearl Harbor.

The request follows reporting by Civil Beat last month that found Navy officials had enough evidence in January to conclude a pipeline attached to its Red Hill fuel facility was leaking fuel into Pearl Harbor, according to Hawaii Department of Health standards. However, officials did not share that information with DOH until May.

Officials learned that the pipeline had failed leak detection testing just days before hearings in which the Navy was arguing its case for a DOH permit. But during those hearings, the Navy never mentioned the leak. In emails, Navy officials worried how the leak might impact their ability to secure a permit from DOH, noting it was a “sensitive time.”

In a letter to Acting DOD Inspector General Sean O’Donnell on Wednesday, Sens. Mazie Hirono and Brian Schatz and Reps. Ed Case and Kai Kahele called for an independent probe.

They want investigators to determine whether Navy officials “delayed investigation or notification out of concern it might influence its ability to secure an extension of Red Hill’s state operating permit,” the letter states.

“Given the gravity of these allegations and the Navy’s dispute of them, an independent inquiry is necessary to ensure integrity and public trust in how the Navy is operating and conducting oversight of Red Hill,” the legislators wrote.

The World War II-era Red Hill fuel facility is made up of 20 underground fuel tanks, each larger than Aloha Tower, and a series of pipelines that use the power of gravity to deliver fuel to Pearl Harbor and the airport, among other locations. The source of numerous documented fuel leaks over several decades, the facility has for many years been a source of intense concern from residents and environmental advocates who worry about the drinking water aquifer located beneath the tanks.

The contested case against the Navy’s permit application is ongoing.

Asked for comment on Wednesday, the Navy’s public affairs team in Hawaii referred questions to the communications staff of the defense department’s inspector general. That office said on Thursday that it received the letter and is reviewing the request.

Hirono, Schatz, Case and Kahele presented several areas of inquiry in their letter.

Among their questions are whether the Navy covered up evidence or delayed informing DOH about the source of its leak to “avoid jeopardizing” the approval of its permit; whether Navy officials were “deficient or somehow negligent” in failing to report the source of the leak earlier; whether the leaking pipeline is considered part of the Red Hill facility; and whether officials “intentionally misled” DOH during the contested case hearing.

They also want to know whether the fuel spill has been cleaned up and whether the Navy was fined or faced other enforcement action.

“We recognize the strategic importance of Red Hill to our national security and expect that the facility is operated safely and in accordance with all federal and state environmental laws and regulations,” the lawmakers said.

“The facts raised by several Hawaii news outlets in recent weeks are extremely troubling, and the Navy’s disputes regarding several of the allegations warrant an independent investigation to restore the community’s trust in how the Navy operates Red Hill.”

They added that if any wrongdoing is uncovered, they expect “appropriate action will subsequently hold those responsible accountable.”

The DOD’s inspector general reports to the secretary of defense. Congress can require the office to launch an investigation if it passes a law to that effect, according to Hirono spokeswoman Martha Spieker, but in this case, the lawmakers are simply requesting that an investigation be opened.

The delegation’s letter follows another message it sent earlier this week to the Navy itself. That letter, addressed to Navy Secretary Carlos Del Toro, stated that the lawmakers are troubled by allegations that officials were “not appropriately forthcoming” about the Pearl Harbor leak.

“The people of Hawaii deserve better from the Navy,” they wrote.