Counter-terrorism officers have launched an investigation after white powder was sent to five Islamic centres, mosques and government buildings in London.
A mosque in Leyton, a Muslim centre in Finsbury Park and another in Tottenham all received packages last Thursday.
Muslim peer Lord Ahmed was also sent hate mail along with the white powder.
A government mail screening service at Newham also received white powder in a package.
Three of the packages were found to be “not noxious or suspicious”, Scotland Yard said.
Aslam Hansa from the Noor Ul Islam Trust in Leyton told the BBC that the envelope felt “suspicious and lumpy”.
She said: “When we opened it we saw it said ‘paki filth’ with a picture of a mosque and there was white powder inside.
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“We have a very good relationship with the local police and they said to call 999.
“We’ve never really experienced anything like this before – it saddens us – but we’re grateful that it wasn’t anything worse and that nobody was hurt.”
Scotland Yard has confirmed that the North East Counter Terrorism Unit is investigating the incidents.
Toufik Kacimi, chief executive of Muslim Welfare House, Finsbury Park, said the building had to be evacuated for more than two hours when the package – which bore a Sheffield postmark – was discovered.
He said: “My colleague tried to open it and a little bit of white powder came out – we thought it could be anthrax.
“There were about 150 people here, so we had to go outside. We had to tell people coming here for prayer to go elsewhere.
“We have never had any trouble before. After the Brexit referendum, the environment is more hostile towards foreigners.”
Mr Kacimi said he received a phone call from Labour Leader Jeremy Corbyn, his local MP, in the wake of the incident.
He said: “He and the police, the local council, they have all been very good. They want us to feel reassured but it is obviously very scary.”
Lord Ahmed told the BBC that the white powder went all over his clothes.
He said: “It was frightening, and I think that even more than it being frightening for me, it was a big shock for everyone who was around me because security personnel came and told everyone to be calm and remain seated, and you could see the police officers with guns.”
There have been no reports of illnesses as a result of contact with the powder.
