Police have arrested a man following reports of concerning incidents across the Metrolink.
A man had allegedly let gas off on trams on the Bury to Victoria line of the network.
Several people reported feeling discomfort or dizziness but no serious injuries were reported.
Officers have now arrested a man in his thirties on suspicion of possessing a noxious substance with intent to injure. He remains in police custody for questioning.
Police are asking witnesses of anything suspicious to report it as an investigation is now underway, but there is not believed to be any wider threat to the public.
Detective chief inspector Paddy Connell said: “We fully appreciate that incidents of this nature can cause concern in our communities, but I want to reassure the public that we do not believe there is any wider threat present.
“We are working hard to establish the full circumstances of the events that have been reported over recent days.
“As officers continue to work their way through all the evidence available, we are asking anyone who has any information to please come forward. This includes anyone who believes they have witnessed something suspicious, or similar to the incidents that we are dealing with.
“Our transport hubs are operating as usual, and I would encourage anyone with any concerns to speak to a police officer, who will be more than happy to discuss any queries you may have.”
You can contact police via 101 or our Live Chat service at gmp.police.uk, or Crimestoppers, anonymously, on 0800 555 111.
