Poor communication within an FBI division led to a delay in how the bureau worked to access the iPhone belonging to the alleged shooter in the December 2015 San Bernardino terror attack.

The revelation is part of a Justice Department inspector general report released Tuesday, which also finds that top FBI officials were truthful when telling Congress that the bureau could not unlock the phone belonging to Syed Rizwan Farook.

The probe was launched after a former senior FBI official expressed concern that the FBI’s Operational Technology Division, or OTD, may have had the ability to access data stored on the phone, but did not use them.

That would have made then-FBI Director James Comey’s testimony to Congress in February and March 2016 — that the FBI needed help from Apple to access data on the iPhone — inaccurate.

The FBI eventually paid a third-party firm to unlock the iPhone in late March after Apple fought back against a court order ordering the company to unlock the device.

Farook and his wife, Tashfeen Malik, killed 14 and injured 22 others at a public service center. They were later killed in a shoot-out with police.

“The OIG has conducted inquiries into the situation, including interviewing relevant key participants, and found no evidence that OTD had the capability to exploit the Farook iPhone at the time of the Congressional testimony and initial court filings,” the report says.

“However, we found that inadequate communication and coordination within OTD caused a delay in engaging all relevant OTD personnel in the search for a technical solution to the Farook iPhone problem, as well as the outside party that ultimately developed the method that unlocked the phone, issues that we learned the FBI has since taken steps to address,” the report adds.

One of the issues was that the head of the FBI’s Cryptographic and Electronic Analysis Unit did not communicate with the head of the Remote Operations Unit within OTD’s Technical Surveillance Section.

The FBI told the IG that there was no delay in unlocking the iPhone, but agreed that it would update OTD protocol regarding how it goes about communicating with other divisions in the future.

In December, FBI Director Christopher Wray told House lawmakers the FBI is struggling to decode private messages on phones and other mobile devices that could contain key criminal evidence and the agency failed to access data more than half of the times it tried during the last fiscal year,