A suspected bomb has been found near a Wolverhampton mosque, making it the third explosive device targeting Muslims in the West Midlands in a month.

Police said traces of an explosion and debris consistent with a detonation were found close to Wolverhampton Central Mosque on Friday.

Counter-terrorism detectives were continuing to question two Ukrainian men, aged 22 and 25, arrested on Thursday in connection with the suspected attempted bombing of a mosque in Tipton last Friday and an attack on a Walsall mosque on 21 June.

West Midlands counter-terrorism unit searched a software company where the two men were believed to have been working on a university placement. They are believed to be engineering students.

Police evacuated streets near the Wolverhampton Central Mosque on Thursday night after receiving information about "a possible device activation".

West Midlands police said specialist officers called in to search the area around the mosque on Thursday had found the "seat of an explosion" and debris on a nearby roundabout. An area around the mosque was sealed off at 8pm as a military bomb disposal team was deployed.

West Midlands police said they were acting on information that an unspecified device had been "activated" on 28 June, as part of their investigation into the bombing campaign.

An officer had spotted and arrested one of the men in Small Heath, Birmingham, which led to the arrest of the second man nearby and the sealing off of roads for searches to be carried out by bomb disposal teams. The pair were being held on suspicion of being involved in the commission, preparation or instigation of an act of terrorism. The arrest of the two men was followed by searches of their home and work addresses on Thursday afternoon.

Clive Martell, chief executive of the software company Delcam, said: "The two men were on work placements with us, but were not employees of the business. They are studying at a foreign university and are engineering students."

Martell told the Birmingham Mail that the men were studying in an eastern European country: "One of the men has been with us for four months and the other has been with us for two months. They were around halfway through the course and we understand that they met each other whilst on the placement.

"This was completely unexpected and we are doing everything we possibly can to assist the police with their investigations."

Assistant Chief Constable Marcus Beale, who is in charge of the investigation, said: "Officers searching the area [around the Wolverhampton mosque] have found the seat of an explosion and debris on the island near the mosque.

"The investigation is being led by specialist officers and staff from our counter-terrorism unit who are being supported by a range of departments from across the force.

"We recognise the impact news of the latest find will have on the communities of Wolverhampton and further afield. We're working hard to complete our inquiries so that the area can be returned to normality.

"While the investigation is in its very early stages, early indications are that the explosion happened on Friday 28 June."

Last Friday, residents were evacuated after a blast near the Kanzul Iman Masjid (mosque) in Tipton left nails and debris scattered outside. Police believe the intention was to kill or maim after the attack in broad daylight. No one was injured but some minor damage to property was reported.

A small component part of the suspected nail bomb was found in a garden nearby and specialist army disposal officers were called to the scene to carry out a controlled explosion.

It came after more than 100 residents were evacuated from their homes in the Caldmore area of Walsall last month after an explosion near the Aisha Mosque and Islamic Centre. No one was hurt in the blast, which caused minimal damage to a wall near the mosque on 21 June.

On Saturday, police will deploy 1,000 officers to deal with an English Defence League protest and a counter-protest by anti-fascists in Birmingham.

Police will be monitoring community tension indicators for signs of any intelligence suggesting disorder.

Timeline: mosque attacks

22 May 2013

Drummer Lee Rigby of the 2nd Battalion of the Royal Regiment of Fusiliers is murdered.

Later that day, a man is arrested following an attempted arson attack on a mosque in Braintree, Essex. Another man is arrested on suspicion of racially aggravated criminal damage following an attack at a mosque in Gillingham in Kent.

23 May 2013

A Milton Keynes mosque is petrol-bombed.

26 May 2013

Firebombs are thrown at an Islamic cultural centre in Grimsby, Lincolnshire. Two men are arrested at the scene by police who were guarding the mosque following an attack there earlier in the week.

4 June 2013

A mosque and community centre in Muswell Hill in north London is burned down in an arson attack.

8 June 2013

128 pupils and staff evacuate Darul Uloom Islamic School in Chislehurst, south-east London, after intruders break in and a fire is started. Four teenagers are later arrested.

18 June 2013

Arson attack on the Masjid-E-Noor mosque in Gloucester. Two men are arrested.

21 June 2013

A small homemade bomb is left outside Aisha Mosque in Walsall, West Midlands.

12 July 2013

A nailbomb is left outside Kanz-ul-Iman Central Jamia Mosque in Tipton, West Midlands.

18 July 2013

Two Ukrainian men arrested in connection to the attempted bombings in Walsall and Tipton.

19 July 2013

Police find traces of an explosion and debris consistent with a detonation outside Wolverhampton Central Mosque.