More on KentOnline
A hate letter filled with white powder warned a mosque "war is coming".
Police are investigating whether the letter, which was delivered yesterday, is connected to two others sent around the county.
Mosques in Canterbury and Gravesend were also targeted, though no powder was in the Gravesend letter.
Police cordoned off the area outside Maidstone Mosque, in Mote Street, after receiving a call at 3.10pm.
Imam Dr Muhammad Usmani said: "We received two letters with the rest of the day's post, I opened one of the letters and read the top and bottom line, I saw "war is coming" was written.
"I noticed there was powder on the paper and put it back in the envelope with the other letter, which I didn't open.
"It didn't bother me, I didn't ring the police, but then I received a message from Canterbury saying their Imam had received been delivered itching powder.
"I called the police then as I realised there could be something dangerous inside the letters."
"We received a similar letter a few years ago with talcum powder in it, we might have had one or two since but none with powder inside."
The cordon outside Maidstone Mosque was in place until 6.10pm, forensic tests revealed the powder was harmless.
A spokesman from Kent Police said: "We are investigating the possibility that three letters sent to mosques on May 2 are linked.
"Enquiries are on-going."
Maidstone and The Weald MP Helen Grant visited the mosque today.
The Tory MP said: "I utterly deplore these cowardly attacks upon our friends and neighbours at Maidstone mosque.
"This vile hatred has no place within our society.
"I know that the people of Maidstone, as well as the other communities impacted across our county, will unite against this vicious bigotry.
"Our open and tolerant community will not allow a small minority to divide us and we will stand together to stamp out racist extremism wherever it rears its ugly head.
"I am ready, like so many others across our town, to support our friends at Maidstone mosque in any way that I can."