Fire crews are battling a blaze which is believed to have started at a souq in the emirate
The fire is believed to have started at the Iranian souq in the emirate at about 6.30pm on Wednesday.
The site is near to Ajman Speciality Hospital and to a fruit and vegetable market in the industrial area.
The cause of the fire is not yet known.
The souq, which is home to dozens of traders, is a popular attraction in Ajman, drawing visitors from across the Emirates.
Rajab Elsawi, who owns the Khadem Fresh Meat store opposite to the souq, said he alerted emergency services after he saw a thick blanket of black smoke develop.
He started to remove road barriers in order to allow fire crews access to the scene.
"It is a one-way road and barriers were placed to stop drivers from travelling against the flow of traffic, so I removed them to facilitate access for civil defence and police vehicles.
"There are dozens of shops in that souq."
Another worker, who asked not to be named, said several people tried to put it out the fire with fire extinguishers from their shops but were unable to contain the rapidly-spreading flames.
They were assisted by crews from Dubai, Sharjah and Umm Al Quwain.Ajman Civil Defence said the blaze had been brought under control at about 9pm.
Major Gen Sheikh Sultan bin Abdullah Al Nuaimi, commander-in-chief of Ajman Police, said investigations were ongoing to determine the cause of the fire.
He said 25 police cars were sent to the scene to support civil defence officers.