Between 2.45am and 3.15am on Sunday, emergency services attended three fires that are being treated as arson. All three were in close proximity to each other and police suspect they are connected.
At 2.48am an old fire appliance, now owned by a demolition company, was parked underneath the Durham Street overbridge near the entrance to the former Rialto cinema. It was broken into and the cab area was set alight.
While the fire service were attending that fire, two further fires were lit a short distance away at about 3.10am. The first was on Manchester Street in a large rubbish skip opposite a motorcycle store.
The second was lit at the front of a truck parked in the driveway of commercial premises in Allen Street, off Manchester Street.
Detective Sergeant Mark Worner says there is no indication that the incidents are connected, "at this stage".
Police are also investigating.
Mr Worner said: "We are encouraging anyone who sees people at unattended premises at a time or in circumstances that don't seem right to contact us immediately.
"If members of the public see any suspicious activity or persons in and around these areas, please contact police immediately."
