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A US police force has suspended the use of a self-deleting text messaging service after an Al Jazeera investigation found it could have been used to conceal evidence.

The Tiger Text application, which permanently and irretrievably deletes messages after a set period of time, was used by officers belonging to the Long Beach Police Department in the state of California.

Serving and former officers told Al Jazeera that police-issued phones had the software installed on them and that it was used to share details of police operations as well as sensitive personnel issues.

Two officers said supervisors told them to use the app to have conversations that would not be discoverable.

All the officers Al Jazeera spoke to requested that their identities be kept secret for fear of reprisals from the Long Beach Police Department.

The revelations have raised concerns that the police force may have used the software to avoid potentially incriminating information being disclosed to courts.

Police in Long Beach had the fifth-highest officer-involved shooting rate in the US per capita in 2015, and the city has paid out tens of millions of dollars to families of those shot.

Al Jazeera spoke to lawyers who said they were unaware that the department was using the software.

The city denies the app was used to conceal evidence. 

In a statement on Tuesday, the City of Long Beach said it was ending use of the software, which had been in use since 2014, after a review initiated by “Public Records Act requests and media inquiries”. 

“Use of the application began when the Police Department transitioned to iPhones, which did not have a built-in secure communication feature sufficient for the needs of the Department,” the city’s statement read.

“The primary purpose of the Tiger Connect [Tiger Text] application was to allow for a continued means of transitory, immediate, and secure communications regarding operational and personnel matters. 

“Police Department employees have been trained to and do document any exculpatory/discoverable evidence in a police report or other formal departmental communication. “

The American Civil Liberties Union (ACLU) believes the use of the software may have breached laws that require records be preserved and disclosed to courts if needed.

Thousands of verdicts could potentially be at risk, according to the ACLU.