One of her staff members who was hospitalised after coming in contact with the package has since been released.
The package was sent to Muslim Labour MP Mohammad Yasin.
Police are investigating another suspicious package sent to MPs' offices in Westminster, the fourth in recent days.
Four Muslim Labour MPs have been sent suspicious packages over the last 48 hours with copies of a "Punish a Muslim" letter that calls for violence against Muslims.
The leaflets, reported in West Yorkshire, Midlands, London, Cardiff, Leicester, Sheffield and Birmingham, carried an image of a dagger with the letters MS, indicating links to so-called Muslim Slayer which targeted mosques in London and the United States a year ago with similar threats, the Mirror reported.
MPs have condemned letters encouraging recipients to take part in "Punish a Muslim Day" as "abhorrent".
Labour MP for Walthamstow, Stella Creasy, said she found out that some of her constituents had received the letters on Friday evening while helping others report anti-Semitic graffiti.
"Today we stand together with those facing this vile Islamophobia, to show them support, care and solidarity".
The package contained a "low-level noxious substance", while the letter is a form one which encourages everything from verbal attacks on Muslims in the street to mosque bombings.
Counter Terrorism Policing North East are coordinating the investigation at this time and will consider any potential links to existing enquiries.
It released a statement, saying: "It is essential that all letters and envelopes are kept and handled minimally to preserve evidence for the police to investigate".
A Metropolitan police spokesman said: 'Police were called at 9.49am on Tuesday, March 13 to reports of a suspicious package at Norman Shaw Buildings, Victoria Embankment, Westminster.
The organization said that some of the letters appear to have been mailed out of Sheffield, the NYT reported.
Parliament has emailed all staff, warning them to "be on the alert for suspicious items of mail".