Federal prosecutors in the US have informed a court in Washington DC that they are currently going through data from nearly hundred smartphones seized from protesters during US President Donald Trump's inauguration.

Since most of the phones were locked, the authorities hacked into them to extract information, which includes private photos, videos, medical data and more. Relevant information from the seized phones is expected to be produced in the court.

Federal officials say they were fully authorised to access the phones and they have obtained a warrant for the search. Some defendants had requested a hearing before the authorities could search their devices and social media, but the judge oversaw that argument, saying that if defendants believed the government carried out an illegal search, they could later ask the court to suppress information.

Data extraction by authorities has increased in the recent past, notably after the San Bernardino case. Although the Federal Bureau of Investigation pressured Apple at the time to give them backdoor access, authorities later resorted to using third-party phone unlocking tools to access the phone.

Israeli firm Cellebrite is reported to be among the leading providers of such software. Although some of the recent models of the iPhone may be difficult to crack, older models and Android devices are easily accessible, according to security experts.

Data privacy and human rights activists have expressed concern over such methods, but authorities defend their move citing national security, especially when a case is related with terrorist threat.