South Yorkshire Police were called out by a member of the public who had heard a load bang to Laughton Common, Dinnington where they recovered the item.
Police recovered the small suitcase on Sunday, October 8, which they believe contained a number of accelerants.
A spokeswoman from South Yorkshire Police said: “Just before 12.40pm on Sunday, October 8, police received a call from a member of the public who claimed to have heard a loud bang at around 5.30am that morning while walking in Laughton Common, Dinnington.
“Officers attended an area of open land, just off Station Road, and found a small suitcase, believed to have contained a number of accelerants.
“The items have since been recovered and are being forensically examined by specialist officers.”
An investigation is now underway and anyone with information should call 101 quoting incident number 453 of Sunday 8 October.