The office of Mumbai Mayor Ritu Tawde got a bomb threat email Friday. The note also named Bollywood actor Amitabh Bachchan and singer Diljit Dosanjh, Hindustan Times and the Indian Express reported. Police said a group calling itself the Khalistan National Army claimed the act, Hindustan Times reported. Checks found nothing odd. Deputy Commissioner Manish Kalwaniya said as much, per Hindustan Times.

The Indian Express said the sender used the name Smith Johnson. The subject line was "Mumbai Bombay Bolega Khalistan Zindabad." The note threatened a grenade attack on Bachchan's house on October 31. It framed the threat as "khoon ka badla." Hindustan Times said the mail threatened the mayor's office at 3 in the afternoon and schools at 1 in the afternoon. It also named Bachchan's Jalsa bungalow in Juhu between October 31 and November 27. The Indian Express said the email warned of a "suicide attack" at Diljit Dosanjh's Mumbai concert at the Mahalaxmi Racecourse on November 27.

Police suspect the same group has sent hoax mails in recent months, Hindustan Times reported. The Indian Express said the message listed names said to be tied to the Khalistan National Army. It also mentioned Babbar Khalsa. Delhi police had already blocked a Diljit concert there over security fears, a police officer said, per Hindustan Times. Mumbai police opened a probe, the Indian Express reported. Security rose around Bachchan's Juhu home after the email named the house.

Police said they are tracing the sender and have stepped up patrols at the named sites, Hindustan Times reported.

What we know: A threat email named Bachchan's home and a Diljit Mumbai concert date. Police searched and found nothing.
What we don't: Who sent the email, and whether any real plot exists beyond a hoax pattern.