Individuals who were arrested in Washington, DC, during protests over the inauguration of Donald Trump have been targeted as part of a social media investigation into their Facebook activity by police.

At least two individuals, who have not been identified, were part of the more than 230 people arrested on January 20 - inauguration day - and charged with felony rioting, which is punishable by up to ten years in prison.

Those who have been charged had their phones seized by DC Police, who have been holding on to the devices since the arrests.

A subpoena issued by the US Attorney's Office for the District of Columbia on January 27, shows police asking Facebook for subscriber information for an arrestee.

Another arrestee received an email from Facebook's 'Law Enforcement Response Team' telling the individual that he or she is part of a social media investigation.

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At least two people who were arrested in Washington, DC, during protests over the inauguration of Donald Trump (pictured above) are now part of a social media investigation

UPDATE: US Dist Attorney of DC & DC police subpoenaed Facebook for account data on numerous inauguration protestershttps://t.co/kpCPEwxLde pic.twitter.com/Nei9RKH089 — George Joseph (@georgejoseph94) February 6, 2017

Rachel Reid, a spokesperson for the DC Metropolitan Police Department, told CityLab that it 'does not comment on investigative tactics' after the site obtained copies of the emails.

Meanwhile, Facebook told CityLab: 'We don't comment on individual requests.'

Depending on which legal process Facebook chose to use for the arrestees depends in terms of how much data they can seize for investigation.

A search warrant would allow Facebook to give away information including 'messages, photos, videos, timeline posts, and location information', according to Facebook's guidlines.

A subpoena, which is what at least one arrestee faces, or a court order would give authorities less information about an individual's account.

It would still, however, include the person's 'name, length of service, credit card information, email address(es), and a recent login/logout IP address(es)'.

IP data points could show where the arrestees were the day of the protests.

Freddy Martinez, director of the Chicago-based police accountability group Lucy Parsons Labs told CityLab that it could even further the prosecution process.

A subpoena could give authorities person's 'name, length of service, credit card information, email address(es), and a recent login/logout IP address(es)'. IP data points could show where the arrestees were the day of the protests

'Asking for IP data could point toward a physical location—i.e. an apartment—that people stayed in and could widen the net for further prosecution of other protesters,' he said.

DC officials have been criticized for the arrests that took place on inauguration day.

Prosecutors have dropped cases against nine individuals since January 20, including four journalists who were arrested while chronicling the actions of a group of self-described anarchists.

Last week, one arrestee's Gmail account showed activity from his or her mobile phone, which is still in police possession.

It's not unusual for authorities to ask social media sites like Facebook and WhatsApp for data about users.

Law Enforcement officials in the United State requested information on the Facebook accounts of 38,951 users between January and June 2016 - the latest data available.

The majority of the requests were through search warrants and subpoenas, according to Facebook's government requests report.

Officials received data information in 80 per cent of cases.