Sarkar Md Kaisar, superintendent of Tangail police (SP), made the disclosure at a press briefing at his office on Friday noon.
He told media that they did not confess to their involvement with the crime during primary interrogation. They will be grilled further and be placed before the victim woman for confirmation.
A notorious gang committed robbery in the Narayanganj-bound Eagle Express coach after it started from Kushtia on Tuesday night.
When the coach crossed the Tangail area, the robbers, who hopped into the coach in the guise of passengers, took control over steering and robbed all the passengers. Later, they raped a woman on the moving bus.