The cash van of a private company engaged in the business of transporting money, was moving towards Mumbai after collecting cash from Mankhurd and Govandi railway stations on Mumbai's Harbour line when the incident took place, police said.
"The driver of the van, manager and one security guard were present in the vehicle when the incident took place near Dhobi Ghat, Mankhurd on Panvel-Sion highway at around 4 pm today," a senior police official said.
The accused, who were armed with choppers and firearms, stopped the van by attacking it with a stick, he said.
Mankhurd police have registered a case under IPC sections 392 (robbery), 427 (mischief causing damage to the amount of fifty rupees) and 34 (common intention) and other relevant sections of the Arms Act, the official said.
Further investigation into the matter is underway, he added.