The police said that they are examining the envelopes.
BJP MP Pragya Singh Thakur on Monday filed a police complaint saying that she received envelopes with poisonous chemicals on them.
The police seized 3-4 envelopes from her residence. Some of them contained letters written in Urdu, they said.
"We got a complaint from the MP that she had received envelopes with some harmful chemicals in them and we are filing an FIR in the matter," Bhopal Deputy Inspector General Irshad Wali told news agency PTI.
When asked about the presence of chemicals in the envelope, he said that it will be clear only after the forensic team examines it.
Meanwhile, a picture of a brown envelope, purportedly with Pragya Thakur's address on it, was being circulated on social media with a message that it contained some poisonous chemical which was life threatening.
Bhopal Superintendent of Police Umesh Tiwari said a case has been registered against an unidentified person.