Counter-terror police are investigating after hate mail and suspicious packages were allegedly sent from Sheffield to mosques in London, South Yorkshire and America.
Handwritten notes were reportedly received by several mosques in the captial, while hate mail was also sent to mosques across several US states and another Muslim place of worship in Rotherham.
All of which bore a Sheffield postmark - with many of them featuring the same pseudonym or initials - and were sent in the last 18 months. The North East Counter Terrorism Unit has now launched an investigation.
An NECTU spokesperson said: "Police received a number of reports of malicious communications and packages which have been received in recent days across London.
“Specialist officers have attended the addresses and the contents of the packages were examined.
"In all cases, the substances were found not to be noxious or harmful.”
Forest Gate mosque, Coventry Cross mosque in Bromley-by-Bow, and Shacklewell Lane mosque - all in London - reportedly received letters last month saying the sender would be visiting the mosques.
Meanwhile in July last year, packages containing white powder were sent to the parliamentary office of Nazir Ahmed, an independent peer from Rotherham.
Three mosques in Leyton, Finsbury Park and Tottenham, as well as the Bank of England, also received packages.
The letters allegedly contained offensive language directed towards Pakistani Muslims.
In addition, a letter threatening to kill Muslims was sent to a mosque in New Jersey, America, earlier this year. And there were others received by mosques in Washington DC, New Jersey, Alabama and South Dakota.
TellMama, a reporting service for cases of anti-Muslim abuse, said similar letters targeted mosques in New York, Georgia, and Kentucky this spring.
Many of the letters reportedly carried the same pseudonym.
We reported in March how the Masjid Bilal in Lexington, Kentucky, received a card containing the words 'An explosive device will be placed at your mosque very soon!' that was posted from Sheffield.
A 'hate' letter was also sent to the Jamia Masjid mosque in College Road, Masbrough, in February.
NECTU specialists are now investigating the possibility that all the letters sent have been sent from the same source.
Contact police with information on 101.