Officers looking for a man who raided a jewellers while wearing a burka are investigating a similar incident.
A man thought to be wearing a burka threatened a security driver in Birmingham on 14 March with what is thought to be a firearm before fleeing.
Last Thursday, an armed robber pushing a child's buggy and disguised as a woman in a burka went to the Friends Jewellers in Smethwick, West Midlands.
He was joined by four other men who smashed cabinets before fleeing.
The burka is a traditional form of Islamic dress for women consisting of a full body covering that also obscures the face.
Police said in the incident on 14 March, the man, "dressed in black and wearing a face covering believed to be a burka", approached the guard outside a supermarket in the Fox and Goose Shopping Centre on Washwood Heath Road.
The weapon, believed to a firearm, was wrapped in a black plastic bag.
The Securicor driver managed to get back into his van and shut the sliding door, trapping the weapon in the door for a few seconds before the offender managed to release it.
The gang sprayed staff with an unknown substance
The man then ran into the passenger seat of a dark coloured Ford Focus, parked by a nearby post office, which then drove off along Bromford Lane.
Following last week's robbery at the jewellers in Cape Hill, the owner has offered an undisclosed reward for any information which leads to a conviction.
Four members of staff were sprayed with an unknown substance before the offenders, armed with hammers, escaped with about £200,000 worth of jewels.
In a statement, police said: "Due to the similar circumstances, officers are exploring possible links with the robbery that took place at Friends Jewellers last week."