ARMED robbers wearing clown masks attacked a worker and stole a safe at a sandwich factory.

One man wielding a sledgehammer and two accomplices carrying hammers burst into Express Cuisine's production plant at Sunnyside Business Centre in Adelaide Street, Daubhill, at just before 7.10pm on Tuesday.

Owner Sohel Patel believes the robbery is part of the craze for people wearing clown faces to carry out offences and he worries there will be more attacks as Halloween approaches.

The gang punched and kicked an employee, then hauled out the safe and drove off with it in the boot of a car.

Mr Patel said: "A black Audi A3 pulled up in our car park with four people inside: the driver and three others.

"The three passengers got out and came into our reception door at very fast speed.

"They were armed with a red and black sledgehammer and DIY-style hammers and had clown masks on and came through into our open plan office area.

"One member of staff, an admin assistant, was punched and kicked and they asked him where the safe is.

"He tried to avoid telling them where it is and they ended up finding the safe anyway.

"They were going through the drawers trying to find the key."

Mr Patel said the gang failed to locate the key and resorted to carrying the safe away.

One of the burglars ran outside and told the driver to reverse the Audi to the front door.

The group loaded the safe into the car boot and drove off but the boot lid sprang open after just a few metres.

The passengers got out of the vehicle and in trying to close the lid accidentally smashed the car's rear window.

Mr Patel said the Audi sped off with the boot half open and the whole incident was over within seven minutes.

He said: "One of them we believe to be an Asian male because of what he said in Urdu: 'Come on, let's go'.

"The other two we believe are white males. They were all in hoodies and clown masks, jogging pants and trainers.

"The admin assistant suffered black eyes, bruised ribs and his legs are hurt quite badly."

Other employees working in the fridge and distribution areas on the other side of the factory did not see or hear the heist.

Mr Patel said the violent raid was the first time the 17-year-old business — which manufacturers pre-packed sandwiches for clients such as supermarkets and universities and relocated to Bolton from Manchester in April — had fallen victim to the crime.

He said: "We have drivers bringing cash in so we assume it was somebody already known to the business or who has been into office and knew cash does come in.

"All our staff are shaken up and we have to take precautions and change some of the processes we have just because of what's happened.

"I'm more worried about the fact Halloween is coming up and people need to be a bit more vigilant because clown masks may be used, and taken advantage of, during trick-or-treating."