A pair of Republican senators pressed the Justice Department’s watchdog Wednesday to explain why he did not inform them last month that the FBI “failed to preserve” five months of text messages between Peter Strzok and Lisa Page.

In a letter sent by Sens. Chuck Grassley and Ron Johnson to DOJ Inspector General Michael Horowitz, the senators said the IG’s office had indicated on Dec. 13 that it possessed every message Strzok and Page sent to each other between Nov. 30, 2016 and July 28 of last year.

However, the Justice Department admitted to lawmakers Friday that it had not preserved any texts that were sent between Dec. 14, 2016 and May 17 of last year. The FBI blamed technical issues, saying the Samsung 5 mobile phones it provided to employees “did not capture or store text messages due to misconfiguration issues related to rollouts, provisioning, and software upgrades that conflicted with the FBI’s collection capabilities.”

Grassley and Johnson wrote to Horowitz that the Justice Department’s statements about the fate of the messages “needs to be reconciled.”

The senators’ letter asks Horowitz to answer nine detailed questions concerning the timeline of the texts — including whether the messages were ever recovered, when Horowitz’s office was notified that the messages could not be found, and whether any texts from other FBI personnel had disappeared over the same time period.

They also asked whether Horowitz’s office had interviewed Strzok and Page about the messages and whether it has the ability to recover federal records that may exist in the officials’ personal email or texting system.

The five-month period of missing messages covers a period of time that includes President Trump’s inauguration, the firings of National Security Adviser Michael Flynn and FBI Director James Comey and the appointment of former FBI Director Robert Mueller as a special prosecutor to investigate alleged Trump campaign collusion with Russian officials during the 2016 election.

Last month, the Justice Department released hundreds of text messages that Strzok and Page had traded early in 2016. Both served for a short period of time on Mueller’s team, with Page leaving over the summer and Strzok being reassigned late last year to the FBI’s human resources division after the discovery of the exchanges with Page.

Fox News’ Catherine Herridge contributed to this report.